To the Editor: Brief extracerebral applications of AC pulsed electromagnetic fields (EMFs) in the picotesla range intensity have been reported beneficial in the symptomatic treatment of patients with multiple sclerosis (MS) with either a relapsing-remitting or a chronic progressive course (Sandyk, 1992, 1994 a, b, 1995 a; Sandyk & Derpapas, 1993 a, b; Sandyk & Iacono, 1993, 1994 a, b; Sandyk & Dann, 1994, 1995. This treatment modality is effective also in the symptomatic management of acute exacerbation of symptoms and has also been shown to stabilize the course of the disease (Sandyk & Derpapas, 1993b; Sandyk & Dann, 1995; Sandyk, in press). The mechanisms by which administration of these EMFs improves symptoms of MS remain elusive. Application of DC EMFs of higher intensities has been shown to alter synaptic conductivity by modifying the release of neurotransmitters through an effect involving changes in transmembrane calcium flux (Bawin & Adey, 1976; Jaffe et al, 1980; Blackman, 1988; Rusovan & Kanje, 1992. In addition, exposure to EMFs has been shown to alter the circadian release of pineal melatonin (Welker et al, 1983; Semm, 1992) which, in turn, influences synaptic neurotransmission and immune mechanisms