To investigate the effects of insomnia on tinnitus severity and to determine how this relationship may evolve with the passage of time.Questionnaires were mailed to patients before their initial appointment at the Oregon Health Sciences University Tinnitus Clinic between 1994 and 1997. These questionnaires requested information pertaining to insomnia, tinnitus severity, and loudness. During their initial appointment, patients received counseling, education, and reassurance about tinnitus; audiometric and tinnitus evaluations; and treatment recommendations. Follow-up questionnaires were mailed to 350 patients 1 to 4 years (mean = 2.3 yr) after their initial appointment at the clinic.One hundred seventy-four patients (130 men, 44 women; mean age 55.9 yr) returned follow-up questionnaires. Although many of these patients improved in both sleep interference and tinnitus severity, a significant number (43) reported on the follow-up questionnaire that they continued to have difficulty sleeping. Reported loudness and severity of tinnitus were significantly greater for this group than for groups of patients who reported that they never or only sometimes have difficulty sleeping. The relationship between sleep disturbance and tinnitus severity became more pronounced with the passage of time.Insomnia is associated with greater perceived loudness and severity of tinnitus. These findings underscore the importance of identification and successful treatment of insomnia for patients with tinnitus.