The relationship between tumour stage, T-lymphocyte subset infiltration and survival was examined in patients with prostate cancer (n=80). On multivariate analysis PSA (HR 2.47, 95% CI 1.27-4.83, P=0.008) and CD4+ T-lymphocyte count (HR 2.29, 95% CI 1.25-4.22, P=0.008) had independent significance. Increased CD4+ T-lymphocyte infiltration within the tumour was stage independent and associated with poor outcome in patients with prostate cancer.