To determine the proportion of patients whose plasma HIV-1 RNA level remains below a detectable level (less than 500/ml) after 24 weeks of study therapy with either 141W94 monotherapy or 141W94 plus zidovudine (ZDV) and lamivudine (3TC). To determine the safety and tolerability of 141W94 monotherapy and the combination of 141W94 plus 3TC in patients with HIV infection.