Records at the USAF School of Aerospace Medicine, Hyperbaric Medicine Division, were reviewed to determine whether a relationship exists between the length of time from development of symptoms of altitude chamber decompression sickness (DCS) to start of compression therapy and the outcome of treatment. During the 5-year period from 1 January 1984 to 31 December 1988, 233 cases of altitude chamber DCS were treated in USAF hyperbaric chambers. Information obtained from each record included age, sex, time from exposure to symptom onset, time from symptom onset to start of compression therapy, time required for resolution of symptoms, and number of treatment failures (failure to resolve during the first treatment dive or recurrence of symptoms after the first dive). Analysis of the data obtained from treatment records reveals a direct relationship between length of delay to treatment with compression therapy and outcome of treatment. Patients successfully treated with a single treatment dive had an average delay to treatment of 10.6 h. Patients that failed treatment after one dive (failed to resolve or recurred) had an average delay to treatment of 18.2 h. The difference between these groups is significant (p less than 0.05). Outcome of treatment was not significantly related to patient age, sex, or type of symptoms. A discussion of factors causing delays in treatment of decompression sickness is included.