BACKGROUND: Prostate cancer is a leading cancer affecting men worldwide. Benign prostatic hyperplasia (BPH) is a common disease of the prostate affecting men as they age, and a risk factor for developing prostate cancer. Lycopene is a member of the carotenoid family, whose strong anti-oxidant properties have been hypothesised to assist in the prevention and treatment of BPH and prostate cancer. The aim of this systematic review was to examine the effectiveness of lycopene for the prevention and treatment of BPH and prostate cancer. METHODS: A search of the MEDLINE, EMBASE, AMED (Allied and Complementary Medicine) and the Cochrane Library databases was performed for published randomised controlled trials (RCTs) comparing lycopene to placebo (or other interventions) for the treatment of BPH and prostate cancer. All included studies were assessed for methodological quality using the Cochrane Collaboration's risk of bias tool. RESULTS: Eight RCTs met the inclusion criteria for this systematic review. All included studies were heterogeneous with respect to their design and implementation of lycopene. Methodological quality of three studies was assessed as posing a 'high' risk of bias, two a 'low' risk of bias and the remaining three an 'unclear' risk of bias. Meta-analysis of four studies identified no significant decrease in the incidence of BPH (RR (relative risk)=0.95, 95%CI 0.63, 1.44) or prostate cancer diagnosis (RR=0.92, 95%CI 0.66, 1.29) between men randomised to receive lycopene and the comparison group. Meta-analysis of two studies indicated a decrease in PSA levels in men diagnosed with prostate cancer, who received lycopene (MD (mean difference)=-1.58, 95%CI -2.61, -0.55). CONCLUSIONS: Given the limited number of RCTs published, and the varying quality of existing studies, it is not possible to support, or refute, the use of lycopene for the prevention or treatment of BPH or prostate cancer.