Adult male CD-1 mice were injected once daily with either saline or cocaine (20 mg/kg, i.p) for five days. After a seven day drug-free period, they were administered either vehicle or the NK-3 receptor antagonist SB 222200 (5 mg/kg, s.c.) 30 mins prior to a cocaine challenge (20 mg/kg, i.p.). SB 222200 administration 30 mins prior to a cocaine challenge did not significantly alter ambulatory activity in saline treated mice, but blocked the enhanced behavioral response to cocaine in mice given repeated cocaine. Data are presented as mean ± SEM; N=7–14 mice/group (* p<0.05).