The murder surfaced immediately after death and gained a wider degree of acceptability when Antonio Salieri was taken ill and confined to an institution more than thirty years later. It subsequently became fashionable to implicate a whole range of suspects in a multitude of devious plots.

Various commentators, especially medical practitioners, who have subscribed to the 'death by natural causes' school have suggested in various biographies and articles that any of the following may have been responsible for the composers demise:

Severe Miliary Disease: Pneumonia: Brights Disease: Deposit on the brain: Apoplexy: Consumption: Rheumatic and Inflammatory Fever: Epilepsy: Uraemia: Renal Failure: Lack of exercise and overwork: Dropsy: Chronic Nephritis: Severe Grippe: Heart Failure: Tuberculosis: Meningitis: Kidney Failure: Encephalitis: Injury (Unspecified): Goitre: Typhoid Fever: Water on the chest: Gastritis: Cirrhosis: Tabes Dorsalis: Typhus: Fractured skull.

Some of these are very imprecise or highly speculative. A number of the symptoms listed, Brights Disease, uraemia, renal failure and nephritis are associated with kidney disease which is now widely accepted as the cause of death. Two major studies in recent years are those of Dr. Carl Bar (Salzburg 1972) and Australian consultant Peter Davies (various 1984-89). Bar, with considerable conviction, proposed that acute rheumatic fever was the underlying cause of death. Davies, while acknowledging that Mozart had suffered from early attacks of rheumatic fever, presented a strong case for the progression to final illnesses as "streptococcal infection - Schonlein-Henoch Syndrome - renal failure - venesection(s) - cerebral haemorrhage - terminal bronchopneumonia".

The latter proposed sequence commences with an infection which gives rise to the Schonlein-Henoch Syndrome (SHS), a complaint identified by two German doctors in the nineteenth century, Lucas Schonlein and Edward Henoch. The condition affects blood vessels in the vicinity of various organs including the kidneys, stomach, lungs and heart. This can have long term affects and although the affliction is chiefly associated with children, Davies has made a case that Mozart developed the Syndrome in 1784 and this resulted in kidney (renal) failure during his last days. This in turn was worsened by blood letting (venesection) which occasioned a brain haemorrhage towards the end and that the immediate cause of death was pneumonia which "usually develops when the patient is already moribund". There where doubts about his diagnosis expressed by medical sources within the Society of the friends of Mozart in New York published in the Musical Times.

Medical standards were comparatively primitive at the time of Mozart's death compared to the latter part of the twentieth century. Nursing did not exist as a profession and approximately 95% of all drugs presently in use were discovered within the last fifty years. Eighteenth century infant mortality rates often exceeded 50%. Mozart and his sister, Nannerl, were the only two survivors from seven children. Four out of six of Mozart's children died in infancy. Leopold Mozart had commented on the results of the practice of foster care in French rural areas which he had witnessed on the streets of Paris. He wrote of the blind, the lame and the mutilated beggars he had seen, the victims of neglect "while the foster-father and his family were working in the fields".

Average life expectancy was less than fifty years and in the month of December 1791 when Mozart died, there was no one above the age of fifty six who died in St. Stephen's parish that same month. The very existence, names, causes, symptoms or cures for many diseases were completely unknown and the diagnosis of illnesses was highly inaccurate. Advances in medicine from the Middle Ages up to the eighteenth century were limited and many primitive beliefs and superstitions prevailed. The belief that a swollen body was also a sign of death by poison as in Mozart's case can be attributed to ignorance.

Amputations without anaesthetics continued until almost the middle of the nineteenth century. The simple stethoscope was unknown at the time of Mozart's death and even the thermometer was not yet regarded as another aid to medical care. Blood letting, the removal of blood from a vein or by leeches attached to the body, was very widespread due to the belief that ill health was usually due to an excess of blood. It was a school of thought in Dublin, Ireland, which achieved nineteenth century eminence by advocating that shock and existing ailments were only worsened by the then prevalent practice of starvation and blood letting. The Dublin Royal College of Surgeons which advocated nourishment instead of the removal of blood was founded in 1784, the same year Joseph II founded his great hospital in Vienna (it is another mark of Joseph's enlightened attitude that this 3000 bed hospital was far advanced for its day with a section for unmarried mothers reached by a private entrance), followed by his medical Surgeons Academy, the Josephinum, in 1785. Under Maria Theresa and Joseph II Vienna had become the major centre for medical learning in Europe and produced renowned names in medicine. The Empresses personal physician Gerhard Van Swieten (1700-72) had published his "Aphorismos De Cognoscendis Et Curandis Morbus" in 1766 and Franz Joseph Gall (1758-1828) was a prominent conductor of experiments in phrenology and the skull.