Spontaneous motor activity and motor coordination were tested in adult female rats after treating with sodium fluoride at 20 or 40 mg/kg dose level daily for 60 days, using an activity chamber and a rota-rod apparatus, respectively. Total protein concentrations were determined in skeletal muscle, liver and serum of similarly treated animals. The activities of total cholinesterase and acetylcholinesterase were determined in blood and brain regions, respectively. Sodium fluoride treatment suppressed spontaneous motor activity. But no change was observed in the motor coordination of these animals. Tissue and serum protein concentrations were decreased. Cholinesterase activity was decreased in the blood and not in brain regions. A failure of sodium fluoride to impair motor coordination indicated that neuromuscular function required for a forced task was not deteriorated in these animals, although skeletal muscles were deprived of protein and blood cholinesterase activity was suppressed. A suppression of spontaneous motor activity suggests that fluoride has, by a central action, inhibited motivation of these animals to exhibit locomotor behavior. A cholinergic mechanism through a change in the activity of acetylcholinesterase may not account for this effect, since sodium fluoride treatment did not alter the activity this enzyme in brain regions. However, an involvement of monoamines may be proposed in view of previously reported finding that excessive fluoride intake has decreased the concentrations of 5-hydroxyindoleacetic acid and increased that of norepinephrine in rat brain.