A double-blind between-group trial was carried out in 50 depressed patients to compare the efficacy of two sustained release forms of amitriptyline--Lentizol and Tryptizol 75. Patients received either Lentizol 50 mg or Tryptizol 75 75 mg each evening for the first week of the trial, and these dosages were then doubled for a further four-week trial period, with the proviso that dosage for individual patients could be maintained at, or altered to, original level where considered necessary by the investigator. Lentizol gave equivalent therapeutic effect to Tryptizol 75 despite the fact that overall dosage was one-third less than in the case of the latter.