This international, prospective, observational study followed 1,438 hypogonadal men who received up to five long-acting intramuscular testosterone undecanoate injections over 9–12 months. Improvements were reported in mental and psychosexual function scores, as well as blood pressure and lipid parameters. After four injections, the proportion of patients with moderate, severe or extremely severe erectile dysfunction decreased from 67% to 19%, and at last observation, 89% of men were 'satisfied' or 'very satisfied' with their treatment.