Study Hypothesis: The addition of selenium supplementation to cotrimoxazole will improve CD4 counts, decrease opportunistic infections, decrease viral loads and delay the need for initiating antiretroviral therapy(ART) in Rwandan adult patients infected with HIV/ AIDS.

Patients will be recruited from two health facilities (Kibagabaga District Hospital, and Kinyinya Health Center in Kigali), Rwanda that offer care and treatment for HIV/AIDS patients. Patients will be recruited during a 3-4 month period. Consenting adults who fit the inclusion criteria will be enrolled and followed for 2 years. Study assessments will occur at enrollment, 6, 12, 18, and 24 months after initiation of selenium supplementation.

Participants will be randomized using a simple randomized block design to receive either cotrimoxazole and selenium or cotrimoxazole and an identically appearing placebo taken once daily for 2 years. Participants who do not return to the clinic as scheduled will be followed up at home.

All consenting patients with CD4 count between 400 and 650 mm3 will be selected because they are at similar immunological level and hence they will not be eligible to start ARV treatment at the study start. The study will look at the efficacy of selenium supplementation to this already compromised group of patients at a similar stage of the disease.

Inclusion Criteria:

• Patients > or = 21 years at enrollment
• Confirmed HIV positive with a CD4 range between 400 and 650 mm3
• HIV+ patients willing to participate in the study and who provide informed consent
• Pre-antiretroviral therapy (Pre-ART) at enrollment in study (not yet initiated ART)
• Willing to practice barrier method of birth control at all times

Exclusion Criteria:

• Patients intending to be transferred out of the clinic catchment area before study ends
• Patients scheduled to start ART
• Moribund patients
• Pregnant women
• Unable or not wanting to commit to barrier method of birth control