Soares, VL, Soares, WF, Zanetti, HR, Neves, FF, Silva-Vergara, ML, and Mendes, EL. Daily undulating periodization is more effective than nonperiodized training on maximal strength, aerobic capacity, and TCD4+ cell count in people living with HIV. J Strength Cond Res XX(X): 000-000, 2020-The aim of this study was to evaluate the effects of daily undulating periodization (DUP) and nonperiodized training (NPT) programs on maximal muscle strength, body composition, aerobic capacity, muscle power, and immune markers in people living with HIV (PLWHIV). A total of 41 PLWHIV were randomly assigned to control (CON [n = 15]), DUP (n = 13), and NPT (n = 13) groups. The DUP and NPT groups performed combined training 3 times a week on nonconsecutive days during 12 weeks, whereas the CON group was asked to maintain their current level of activity. After the 12-week training program, DUP produced greater gains in muscle strength (except for bench press), V[Combining Dot Above]O2peak, and muscle power than NPT (p < 0.05). Compared to CON, the training groups showed significantly (p < 0.05) increased muscle strength (DUP = 31.0 ± 13.9 kg; NPT = 17.7 ± 9.2 kg; CON = -0.3 ± 1.5 kg), fat-free mass (DUP = 1.9 ± 1.5 kg; NPT = 1.4 ± 1.9 kg; CON = -0.1 ± 1.2 kg), and metabolic equivalent (DUP = 2.3 ± 1.3; NPT = 1.8 ± 1.9), and decreased body fat mass (DUP = -2.1 ± 1.6 kg; NPT = -1.4 ± 1.5 kg; CON = 0.1 ± 0.2) and functional aerobic impairment (DUP = -35.9 ± 17.0%; NPT = -25.8 ± 22.0%; CON = 0.8 ± 3.0%). There was an increase in TCD4 cells only in the DUP group (p < 0.05). The training effect generally provided a positive correlation between change in leg press strength (r = 0.393, p < 0.05), triceps pulley strength (r = 0.417, p < 0.05), lat pull-down strength (r = 0.459, p < 0.05), and muscle power (r = 0.324, p < 0.05) with changing CD4 + lymphocyte count. Daily undulating periodization protocol showed to be safe, applicable, and more efficient for increasing strength, aerobic capacity, and TCD4 cells compared to NPT in PLWHIV.