One group of 10 young subjects were tested twice; in one test session 2 mg lormetazepam, in the other session placebo was administered, in random order. One subject dropped out. In one test session contractile force measurements were made six times; one measurement took place before treatment and the other measurements after treatment with the study medication. Each measurement of contractile force consisted of pushing weights of 0 to 10 kg and exerting maximal force. The corresponding electromyogram (EMG) of the gastrocnemius muscle was recorded. For the forces of 0 to 10 kg the regression was established of EMG on contractile force. Treatment effects on memory were investigated by means of a selection of tests, covering short‐term and long‐term memory, in terms of recall and recognition. Analyses of covariance were performed on the regression coefficients of EMG/ contractile force and on the data of maximally exerted force, the pre‐treatment scores serving as covariate. These analyses did not result in any difference for the two treatment conditions, leading to the conclusion that the administration of lormetazepam did not have any direct action on the contractile systems of human muscle. The t‐tests performed on the memory data resulted in a significant impairment of performance on the long‐term memory tasks, whereas short‐term memory was not impaired. It is concluded that, in accordance with previous research, the administration of lormetazepam results in an impairment in the acquisition of new information in long‐term memory, but also in impaired retention. Copyright © 1989 John Wiley & Sons, Ltd.