STUDY DESIGN: Prospective randomised controlled study. OBJECTIVE: To evaluate the effects of repeated ejaculation on semen characteristics following spinal cord injury (SCI) in a prospective randomised controlled study. SETTING: Spinal Research Centre, Stanmore, UK and Institute of Urology and Nephrology, London, UK. METHODS: A total of 74 patients with SCI above T10 were tested by vibro-ejaculation using a Ferticare penile vibrator (Multicept A/S Horsholm, Denmark) using a standardised technique. The ejaculate was examined according to WHO protocol. The successfully vibro-ejaculated subjects (n = 32) were randomised into a study group (n = 18) and a control group (n = 14). The patients in the study group vibro-ejaculated weekly for 3 months with semen analysis performed at baseline and then monthly. The control group vibro-ejaculated at baseline and at the end of the 3-month period. Two experienced observers performed the semen analysis independently. All measures were compared for statistical significance across the two groups at the beginning and at the end of the 3-month period using a two-tailed student t-test. Significance was determined at the 95% confidence interval (P < 0.05). RESULTS: In total, 10 patients in the study group and nine in the control group have completed the study so far. Six patients have dropped out of the study group and three from the control group for varied reasons. Two patients are currently enrolled in the study and control groups. The morphology and forward progression of sperm shows a statistically significant increase in the study group. The motility improves but is not statistically significant in the study group. No significant adverse effects were reported. CONCLUSIONS: We have shown in this unique randomised controlled study that repeated ejaculation does improve the sperm characteristics in SCI patients. It is suggested that SCI men should undergo repeated ejaculation for at least 3 months before trying intravaginal or intrauterine insemination techniques. If this fails then in vitro fertilisation can be used. This method promotes natural conception, is intimate and cost effective.