Clinical trials conducted in general practice are more especially interesting as they enable to test a drug in the real conditions of use. On the other hand, these trials are beneficial to the G.P. (new image, rupture of his loneliness, change in his prescription habits, contact with hospitals). The methodology, as for hospital studies, must be rigorous. As a matter of fact, these two types of studies are additional and the cooperation between the G.P.'s and the pharmaceutical industry can conduct to the solution of specific problems: drug interaction--long-term therapeutic effect--new indications. This double blind cross over study comparing triazolam and nitrazepam conducted by G.P.'s on insomniacs is the first French clinical study intended for the registration application and done according to this methodology. This work is an exemple of the new opportunity offered to G.P.'s in future. The results have shown that: on 54 patients (23 male and 31 female) of an average age: 48, 32 have preferred triazolam, 13 have preferred nitrazepam, 9 have had no preference.