A prospective semi-longitudinal study was undertaken to determine if urinary neopterin was a predictor for survival in HIV-positive patients. One hundred and one HIV-positive subjects attending a department of genitourinary medicine over a 41-month period were included. Survival data were analysed 6 months after the end of recruitment. Ninety-two subjects were followed up for a minimum of 6 months. Survival figures at 1 and 2 years were 93% (SE 3%) and 79% (SE 5%). There was an inverse relationship between urinary neopterin excretion and 1 and 2-year survival. Two-year survival fell from 70% (SE 6%) for neopterin levels > or = 300 mmol/mol creatinine to 25% (SE 9%) for levels > or = 700 mmol/mol creatinine (P < 0.001). Urinary neopterin may be a useful non-invasive technique in predicting survival in HIV-positive patients.