Sexuality in patients with amyotrophic lateral sclerosis (ALS) has received little attention so far. Although sexual function is not directly affected by the disease process, several patients have reported problems within their sexual relationship. We performed a questionnaire survey to ascertain the extent and clinical relevance of sexual problems experienced by patients with ALS and their partners. Of 91 patients and partners asked, 62 agreed to participate in the study. Compared with the time before disease onset, sexual interest had decreased from 72% to 44% for patients and from 78% to 44% for partners. Sexual activity had moderately decreased from 94% to 76% for the patients and from 100% to 79% for the partners. Before the disease, 19% of the patients and 20% of the partners reported sexual problems. This increased to 62% of the patients and 75% of the partners at time of survey. The problems reported were mainly decreased libido, passivity of the partner and own passivity. The most frequent reasons for these problems were the physical weakness and the body image changes due to ALS. The data show that sexuality is an important and problematic issue for a large proportion of ALS patients and their partners. This topic is rarely discussed in the medical setting. Counselling and information should be made available in order to better address this important aspect of quality of life.