To compare the efficacy of lamivudine (3TC) and zidovudine (AZT) in combination versus the better of didanosine (ddI) monotherapy or ddI/AZT combination, in symptomatic HIV-1 infected children who received less than 56 days of prior antiretroviral therapy. To evaluate the safety and tolerance of 3TC/AZT in this patient population. To determine other measures of diseases in response to the study regimens.