(5-Amino-1,3-dimethyl-1H-pyrazol-4-yl)(2-fluorophenyl)methanone (1) was found to have an antipsychotic-like profile in behavioral tests predictive of antipsychotic efficacy but, unlike available antipsychotic agents, did not bind in vitro to dopamine receptors. Upon further evaluation, 1 was found to cause clonic seizures in aged rodents. An examination of related structures revealed that 5-(substituted aminoacetamide) analogues of 1 shared this novel pharmacology and did not cause seizures. The synthesis and pharmacological evaluation of this series of compounds are described. Two compounds, 2-(diethylamino)acetamide (25) and 2-[[3-(2-methyl-1-piperidinyl)propyl]-amino]acetamide (38), were selected for examination in secondary tests. Like known antipsychotics both compounds reduced spontaneous locomotion in mice at doses that did not cause ataxia and inhibited conditioned avoidance selectively in both rats and monkeys. Unlike known antipsychotics neither 25 nor 38 elicited dystonic movements in haloperidol-sensitized cebus monkeys, a primate model of antipsychotic-induced extrapyramidal side effects. Biochemical studies indicated that these compounds act via a nondopaminergic mechanism. Neither 25 nor 38 bound to dopamine receptors in vitro or caused changes in striatal dopamine metabolism in vivo. In addition, they did not raise serum prolactin levels as do known antipsychotics. Although adverse animal toxicological findings have precluded clinical evaluation of these agents, the present results indicate that it is possible to identify at the preclinical level nondopaminergic compounds with antipsychotic-like properties.