Effects of 1-aminocyclopropanecarboxylic acid (ACPC), a partial agonist of glycine(B) receptors, on the expression and development of sensitization to the locomotor activity of amphetamine (AMPH, 2.5 mg/kg) were studied in mice. ACPC in doses of 100-400 mg/kg did not affect the expression of AMPH sensitization. Combined injections of ACPC (200-400 mg/kg) and AMPH during the development of sensitization did not change the expression of sensitization to the challenge dose of AMPH 3 days after the drug withdrawal. Acute administration of ACPC, 400 mg/kg, enhanced the locomotor hyperactivity induced by a single dose of AMPH, that effect being probably connected with its own stimulatory action of that dose of ACPC. Summing up, our results show that ACPC affects neither the development nor the expression of AMPH sensitization in mice.