The results of a double-blind, randomized, therapeutical trial with SER282, an antidiencephalon immune serum (Serolab, Lausanne, Switzerland), in 36 women, aged 24-56 years, with primary fibromyalgia are presented. Treatment was ambulatory and consisted of either SER282 (20 mg/ml) or amitryptiline (AMI, 50 mg) or placebo (PL) over an 8-week treatment course. Clinical and sleep EEG polygraphic data were obtained at baseline and after 4 and/or 8 weeks of therapy. Compared to an important PL response and moderate analgesia with AMI, pain and associated symptoms improved moderately with SER282. In contrast, polysomnographic recordings showed that SER282 tended to promote stage 4 sleep, while AMI and PL had few – if any – effect on sleep. These results are discussed together with the clinical characteristics of the patients and the relations between pain, associated symptoms, and sleep parameters in our patient populat