This study compares the safety and efficacy of 1592U89 in combination with 3TC and ZDV versus control therapy with 3TC and ZDV alone. If a patient has two consecutive HIV-1 RNA measurements of >= 400 copies/ml (performed at least one week apart) he or she has the option to switch to open-label therapy with 1592U89/3TC/ZDV, to receive the remaining randomized treatment, or to discontinue study medication. If this criterion is not met, patients continue their randomly assigned therapy until the last patient has completed 48 weeks of therapy. Once patients enter the open-label phase, investigators may add or substitute non-nucleoside reverse transcriptase inhibitors, nucleoside reverse transcriptase inhibitors, or protease inhibitors for 3TC and/or ZDV according to their standard practice once patients enter the open-label phase.