The purpose of this study is to see how often Pneumocystis carinii pneumonia (PCP) occurs in HIV-positive patients who have stopped taking medications that help prevent PCP.

The risk of developing PCP may be decreased when an HIV-positive patient's CD4 cell counts (cells of the immune system which fight infection) are more than 200 cells/mm3. This study looks at whether it is acceptable to stop PCP prevention treatment in these patients.

The risk of developing PCP may be decreased with treatment-induced recovery of CD4 counts to > 200 cells/mm3. Few data exist to confirm or negate the continued necessity of PCP prophylaxis for such patients. This study will assess the effects of discontinuing therapy.

Subjects are asked to discontinue PCP prophylaxis if antiretroviral therapy has resulted in a sustained CD4 increase greater than 200 cells/mm3 on two measurements at least 12 weeks apart. They will be evaluated for symptoms and CD4 counts every 8 weeks as well as plasma for HIV-RNA every 16 weeks for 18 months. Subjects whose CD4 count falls to less than 150 cells/mm3 or between 150 and 200 cells/mm3 will have the CD4 count re-evaluated immediately or within 4 weeks. If the second CD4 count is less than 200 cells/mm3 for either case, conventional PCP prophylaxis will be resumed and the subject will be followed on study. Subjects will be followed during study by physical exams and laboratory tests at Weeks 4, 8, and every 8 weeks thereafter.

Inclusion Criteria

You may be eligible for this study if you:

• Are HIV-positive.
• Have had 1 CD4 cell count of less than 100 cells/mm3 and have never had PCP, or have had at least 2 CD4 cell counts over 200 cells/mm3 and have had PCP within 6 months prior to study entry.
• Have received PCP prevention medication within 3 months of study entry.
• Are at least 13 years old (need consent if under 18).
• Are taking anti-HIV (antiretroviral) medication at study entry.

Exclusion Criteria

You will not be eligible for this study if you:

• Have active PCP or symptoms of PCP within 2 weeks of study entry.
• Have a fever lasting more than 2 weeks.
• Have oral candidiasis (thrush).