We prospectively collected data on deaths in the Edinburgh City Hospit
al HIV cohort of patients (60-70% acquired via injection drug use) fro
m October 1986 to September 1994. Sixty-four patients (25% of all HIV
deaths or 2.5/100 person-years) had died without an AIDS diagnosis, an
d 42 (66%) of these had autopsy data available. Some pre-AIDS deaths (
20% or 0.5/100 person-years) were the expected consequence of underlyi
ng medical conditions diagnosed during life: the remainder (80% or 1.9
8/100 person-years) were sudden or unexpected. Examining the underlyin
g conditions, drug overdoses accounted for 45% or 1.1/100 person-years
; bacterial sepsis, 25% or 0.6/100 person-years; liver disease, 26% or
0.6/100 person-years; and an undiagnosed AIDS condition, 9% or 0.2/10
0 person-years. Drug overdoses were the commonest cause of pre-AIDS de
ath in this cohort of patients predominantly infected via IDU, but man
y of the sudden deaths had significant underlying pathology, which may
have increased their susceptibility to an overdose of drugs. In futur
e, death before an AIDS diagnosis should be classified into Medical or
Expected Non-AIDS (MNA or ENA) and Sudden Non-AIDS (SNA).