A review of trekking deaths from 1984 to mid-1987 showed a death rate of 15/100,000 trekkers. Altitude sickness deaths accounted for 3/23 (13%) of these deaths. Recently, we followed up on our original study by compiling the number and causes of trekking deaths in Nepal from mid-1987 through 1991. The overall number of deaths was 40, out of 275,950 trekkers (death rate 14/100,000). Illness accounted for 14 deaths, trauma was the cause of 12 deaths, altitude sickness was the cause of 10 deaths, 3 people were found dead after being reported missing, and one person is still missing and presumed dead. Eight out of 10 altitude sickness deaths occurred in organized trekking groups, even though only 40% of trekkers trek in organized groups. Four people were reported to have died from heart attacks, and 3 people died from apparent diabetic ketoacidosis above 4000 meters in altitude. Trekking in Nepal is a relatively safe holiday that currently attracts more than 60,000 people each year. Monitoring the causes of death among trekkers can help generate advice that could make trekking even safer.