Recent research has shown significant adverse effects of chronic low back pain on sexual activity in 46% of patients. To establish whether and how chronic low back pain adversely affects sexual activity, a questionnaire-based study was conducted on a patient group (low back pain) and a comparison group (neck pain). Patients were administered a visual analog scale, a series of conventional questionnaires, and a specifically designed sexual activity questionnaire covering frequency of intercourse before and since onset of pain, discomfort during intercourse, satisfaction with sexual life, and comfortable and uncomfortable basic coital positions. Patients with low back pain reported more interference than did patients with neck pain, and women with low back pain were more affected than men. Compared with the other groups, women with low back pain had greater reduction in frequency of intercourse, more marked discomfort during intercourse, and more interference with their sexual lives. The most pain generating position was prone for both genders, and the most comfortable one was supine. Sexual impairment, more marked in women, seems to be related to the triggering of pain by intercourse and to psychologic factors.