We characterized the viral dynamics of human immunodeficiency virus (HIV) type 1-infected adolescents receiving highly active antiretroviral therapy regimens (lamivudine [3TC]/zidovudine [ZDV]/efavirenz [EFV], 3TC/ZDV/nelfinavir [NFV], or other regimens) and studied the relationship of viral dynamics with baseline factors and virological responses. Viral decay rates for 115 evaluable subjects were estimated from a viral dynamic model. Viral dynamics in HIV-1-infected individuals aged 12-22 years were similar to those of HIV-1-infected adults and infants. Individuals who received 3TC/ZDV/EFV had a more rapid phase 1 viral decay rate than those who received 3TC/ZDV/NFV or other regimens. Phase 1 viral decay rates were positively correlated with baseline RNA levels and week 1 virus load reductions. Our findings indicate that the 3TC/ZDV/EFV regimen may be more potent than 3TC/ZDV/NFV or other regimens and that early viral dynamics or week 1 virus load reduction measurements may be useful in evaluating the potency of antiretroviral regimens.