The present study tested cognitive-behavioral therapy (CBT) for insomnia in older adults with osteoarthritis, coronary artery disease, or pulmonary disease. Ninety-two participants (mean age = 69 years) were randomly assigned to classroom CBT or stress management and wellness (SMW) training, which served as a placebo condition. Compared with SMW, CBT participants had larger improvements on 8 out of 10 self-report measures of sleep. The type of chronic disease had no impact on these outcomes. The hypothesis that CBT would improve daytime functioning more than SMW was only supported by a global rating measure. These results add to findings that challenge the dichotomy between primary and secondary insomnia and suggest that psychological factors are likely involved in insomnias that are presumed to be secondary to medical conditions.