OBJECTIVE This study investigated (1) the effect of a progressive resistance training (PRT) program and whey protein intake on maximal muscle strength in human immunodeficiency virus (HIV)-infected individuals receiving antiretroviral therapy (ART) and (2) alterations in maximal strength 12 wks after the cessation of PRT with continued supplementation. METHODS Sixty HIV-infected individuals were recruited. Whole body PRT was performed twice weekly for 12 wks. Participants received, in a double-blind placebo controlled manner, either 20 g whey or placebo (maltodextrin) before and immediately after each session. Both PRT groups continued to take either whey protein or placebo for a further 12 wks following the exercise intervention to examine the effects of detraining. RESULTS Forty participants (mean and standard deviation (SD) age 40.8 (±7.7) years, weight 70.8 (±16) kg, body mass index (BMI) 30.9 (±7.2) kg m2); whey protein /PRT (n = 13), placebo/PRT (n = 17), and a control group (n = 10) completed the study. A significant main effect for time occurred for the bench press (p = 0.02), the squat (p < 0.0001), the deadlift (p = 0.001) and the shoulder press (p = 0.02) one-repetition maximum (1RM) in the intervention groups. CONCLUSIONS The PRT program increased maximal strength regardless of whey protein intake. The detraining period demonstrated minimal strength loss, which is beneficial to this population.