At his death from a feverish illness whose precise nature has given rise to much speculation (he was not poisoned), he left unfinished the Requiem, his first large-scale work for the church since the c Minor Mass of 1783, also unfinished; a completion by his pupil Süssmayr was long accepted as the standard one but there have been recent attempts to improve on it. Mozart was buried in a Vienna suburb, with little ceremony and in an unmarked grave, in accordance with prevailing custom.
Mozart may have died of a number of illnesses. The official diagnosis was miliary fever, but the truth is that the physicians who attended him were never quite sure what Mozart died of. He suffered from rheumatic pain, headaches, toothaches, skin eruptions, and lethargy. A common theory today is that Mozart died of uremia following chronic kidney disease. Another possibility is rheumatic fever. Regardless of the cause, Mozart became bedridden for the last two weeks of his life. He died at shortly after midnight on December 5th, 1791, aged thirty-five years, eleven months, and nine days.