Electroencephalographic (EEG) studies were conducted in 40 chronic schizophrenic men and women participating in a 3-month haloperidol (HAL), clopenthixol (CX), and chlorpromazine (CPZ) double blind placebo-controlled study. Of these 40 patients, 13 were on HAL, 9 on CX, 8 on CPZ, and 10 on placebo (PL). Despite some suggestive differences, the overall EEG measures of these drugs were similar, paralleling in this respect their similarity in overall clinical effectiveness despite their chemical differences.