It has been well documented that depression can lead to insomnia. However, evidence from previous research and from clinical experience indicates that the reverse can also be the case: long-standing insomnia can often lead to depression. The aim of this study is to test the hypothesis that, for many people suffering from both depression and insomnia, treating the insomnia successfully without medication can lead the depression to lift as well. The sample consisted of 86 consecutive patients or clients who presented as suffering from chronic insomnia. Two thirds of these people were also suffering from depression at intake. During an initial hour-long interview, self-report estimates of key sleep parameters were recorded, and the Beck Depression Inventory was administered. Subjects were then introduced to the "Sleep Better Without Drugs" self-help program (a book and three audio cassettes), which they used at home to improve their sleep. At follow-up, six to eight weeks later, the sleep parameters were recorded again and the Beck Depression Inventory was re-administered. Results showed that 70% of the insomnia sufferers who were depressed before treatment and learned to sleep better were no longer depressed, or were significantly less depressed, once their sleep had improved. By contrast, among people who did not learn to sleep better, none experienced a significant reduction in depression. The conclusion is that, for many people who suffer from both depression and insomnia, treating the insomnia successfully without medication can eliminate or significantly reduce the depression.