This study evaluates the validity of the last-7-day, self-administered version of the International Physical Activity Questionnaire (IPAQ) long form in HIV-infected people, using accelerometry as the objective criterion. The ActiGraph GT1M accelerometer was worn during all waking hours for 7 days, and the IPAQ was completed on day 7. A total of 30 men were recruited as participants from the Alfred Infectious Disease Clinic, Melbourne, Australia. Self-reported total number of metabolic equivalents minutes per week correlated moderately with accelerometer total activity counts (r = .41, p = .02). However, mean differences showed overreporting with the questionnaire; 546.63 min/wk (95% confidence interval: 217.1-871.2 minutes) for moderate and 295.33 min/wk (95% confidence interval: 88.08-502.6 minutes) for vigorous activity. The IPAQ correlated with accelerometry, but substantial overreporting occurred. The tool may be useful in screening physical activity but should not be used to determine precise levels.