The serum and CSF proteins were analyzed by isoelectric focusing in 16 male alcoholics after alcohol intoxication and after 10--14 days of alcohol abstinence. An abnormally marked protein band with pI 5.7 was found in serum in 15 patients and in CSF in 12 at the first examination. On crossed immunoelectrofocusing it appeared as an increased, cathodal, microheterogeneous molecular form of transferrin. The abnormality was reversible and decreased or normalized in serum in all cases after abstinence. In 6 patients with clinical signs of cerebellar degeneration, an abnormal microheterogeneous pattern of CSF transferrin of partly different appearance to that in serum remained after abstinence. Disturbed liver synthesis of transferrin is a probable origin of the serum finding, which may be specifically related to alcohol abuse. Substitution or loss of acidic amino acids and/or decreased iron binding ability are possible structural explanations.