THE results of previous studies with normal subjects in our laboratory suggested that 1,000 mg of chloral hydrate (Noctec) and 30 mg of flurazepam (Dalmane) were effective in enhancing sleep: chloral hydrate appeared to induce sleep while flurazepam induced and maintained sleep.1 The aim of the present study was to further evaluate the effectiveness of 1,000 mg of chloral hydrate and 30 mg of flurazepam by using insomniac subjects and a two-week drug administration period as part of a 22-night protocol. This contrasted with our previous use of normal subjects and a three-night drug administration period as part of an eight-night schedule. The use of insomniac subjects provides a clear-cut way in which to study the effectiveness of sleep medications. The two-week drug administration period provides not only a more rigorous evaluation of whether drugs produce sleep stage alterations, but also allows for the determination of the length