The effects of apomorphine, Dopa and haloperidol on the competitive behavior in a straight runway of genetically selected Winner-Runway rats (WRS rats), Loser-Runway rats (LRS) and non-selected rats were studied. Apomorphine significantly increased the percentage of winning in nonselected rats competing against WRS rats. In another experiment LRS rats which lost 100 percent of the contests against WRS rats, achieved 50–60 percent of wins when under apomorphine or Dopa effects. When retested without drugs they were again defeated. In pairs made up by two nonselected rats, haloperidol blocked the increase of winning induced by apomorphine. Use of the terms winning and losing instead of dominance and submission to describe the competitive behavior of rats in the straight runway is discussed.