Four groups of four rats each received Noyes food pellets containing 0%, 7.5%, 10%, or 15% NaCl on a fixed-time (FT) 60-sec food reinforcement schedule. Relative to fluid intake levels in the baseline sessions that preceded and followed the FT schedule, water consumption in the FT 60-sec condition increased dramatically. Water intakes for the three NaCl groups differed significantly from the no-NaCl group only in the FT condition, but did not differ among NaCl groups under any condition. It is concluded that schedule-induced polydipsia is not explicable by appeals to underlying physiologically mediated response mechanisms.