The effect of a nutritional supplement on the immune status and haematological parameters of HIV-positive/AIDS patients is tested using standard procedures. This clinical trial of 35 patients consists of a baseline visit and three months of supplementation from April to September 2003. Results showed that viral load decreased significantly (P<0.002) with time following supplementation. Mean cell volume (MCV) and mean cell haemoglobin concentration (MCHC) increased significantly (P<0.002 and P<0.0002, respectively), reflecting the positive effect of the supplement on these haematological parameters. Supplementation had no effect on CD4+ T-cell count, which decreased significantly with disease progression. Owing to certain limitations of the study (small sample size, short duration and the late stage of HIV infection), further studies are needed to confirm the effect attributed to the supplement.