New and recent evidence (see references 1-12) shows that cotrimoxazole (CTX) preventive therapy is associated with a 25-46% reduction in mortality in sub-Saharan Africa, even in areas with high bacterial resistance to the antibiotic. CTX preventive therapy also decreases the frequency of clinic visits and hospitalisations, improves weight and reverses the decline in CD4-lymphocyte counts and the rise in HIV viral loads. Efficacy seems to be maintained over the 1-2 year follow-up periods of the studies. CTX preventive therapy in Africa has few adverse reactions and there are high levels of adherence. In summary, CTX is a safe, cheap and readily available anti-microbial agent, which can extend and improve the quality of life.