The aim of this investigation was to evaluate EEG sleep, especially measures of delta-wave sleep, during and after the administration of somatostatin (SRIF). Eleven normal men, ages 22-37 yr, were administered saline or SRIF (0.1 microgram/kg/min IV) over 160 min at bedtime. SRIF delayed sleep-related growth hormone (GH) secretion without altering the amount of GH available during the entire night of sleep. No changes in delta-wave sleep occurred during either the first 100 min of sleep or the remainder of the night. Furthermore, all major EEG sleep variables were not significantly different between the saline and SRIF infusion night. It would not appear that the peripheral administration of this dose of SRIF or the subsequent delay of GH release has quantitative effects on EEG measures of all-night sleep.