Yawning is a contagious event that occurs alone or associated with stretching and/or penile erection. The aims of the present study were to compare acute and chronic effects of opiates and dopamine on yawning, penile erection and genital grooming behaviors in male Wistar rat. Sixty four male rats were divided into eight groups and received, normal saline (control group), Apomorphine-HCl (Apo, 0.08 mg/ kg), haloperidol (Hal, 0.1 mg/kg), naloxone-HCl (Nal, 1 mg/kg), morphine-HCl (Mor, 5 mg/kg), Apo +Nal, Apo+Mor or Nal+Hal. After acute phase (day 1) and the chronic phase (day 14), rats were observed for the entire duration of the experiment (60 min) at 10-min intervals in order to count penile erection, yawning episodes and the time spent on genital grooming. Previous administration of morphine and naloxone inhibited and increased the apomorphine effects, respectively (P<0.05). Also, naloxone and morphine were adverse and the previous acute administration of haloperidol decreased the naloxone effect; but previous chronic administration of haloperidol increased the naloxone effect. Our findings may explain the opiates and dopamine roles on yawning, penile erection and genital grooming behaviors in rat as a model for human studies.