Patients are randomized to a decision making strategy for initiating or changing therapy based on current clinical practice alone vs. decision making based on plasma HIV RNA quantitation in addition to current clinical practice in patients with <= 300 CD4+ cells/mm3. All patients in the RNA arm as well as a subset (n = 183) of those in the CCP arm will have a plasma HIV RNA quantitation drawn every 4 months. The results of these quantitations will be blinded until the end of the study. CD4 counts will be obtained at least every 4 months if the previous count was > 20 cells/mm3. The remaining patients in the CCP arm will have CD4 counts obtained according to their clinicians' current clinical practices. Medications, clinical status, and changes in antiretroviral therapy will be recorded for all patients in the study. Patients are stratified by CD4+ cell count (<100 cells/mm3 [200 patients] vs. 100-300 cells/mm3 [900 patients]).