233 Background: Studies show a range of environmental and genetic associations with testicular cancer, specifically testicular dysgenesis, increased height, and multiple dysplastic naevi. To confirm these findings, we studied a cohort of testicular cancer patients and healthy controls. We also studied a cohort of unaffected relatives of patients to identify if any noted differences might be due to shared genetic/environmental background. Methods: We identified index cases from the hospital database. They nominated an unaffected relative and an unrelated friend. Controls were supplemented by recruitment of institutional staff. Results: 183 index cases (IC), 57 unaffected relatives (UR) and 103 unrelated controls (UC) were identified. Mean age was 47 years (25-78) IC, 44 years (18-74) in UR and 42 years (20-74) in UC. IC treated by chemotherapy (ch) had higher mean FSH than non chemotherapy patients (s)[18.98 v 13.22 (p=0.01)] and lower mean testosterone [ch:12.21, s:13.52 (p=0.04)] though mean LH [ch:7.94, s:6.05 (p=0.10)] and BMI (ch:27.38 s:26.81 (p=0.33) were not significantly different. Conclusions: In contrast to other studies, we found both testicular cancer patients and their relatives were shorter and with reduced arm length compared with controls; a sign of a possible shared genetic or environmental effect. There was no significant difference in weight, BMI, body fat %, lean body mass, and leg length. FSH and LH were significantly elevated and testosterone reduced in index cases (but not relatives) particularly in those who had chemotherapy. The lack of difference between relatives and controls suggests these are most in keeping with direct treatment effects. [Table: see text] No significant financial relationships to disclose.