To determine if the sexually dimorphic area (SDA) of the gerbil hypothalamus affects male sexual behavior through its projections to the retrorubral field (RRF) or ventrolateral periaqueductal gray (PAGvl), these pathways were lesioned asymmetrically. Unilateral radio frequency lesions of the lateral SDA (ISDA), the major source of the pathways, impaired mating when combined with contralateral RRF, but not PAGvl, lesions. N-methyl-D-aspartate (NMDA) lesions of the medial SDA, ISDA, and the area between them (the total pathway source) eliminated mating when combined with contralateral, but not ipsilateral, NMDA lesions of the RRF. To determine if A8 cells contributed to these effects, males received NMDA in the SDA and NMDA or 6-hydroxydopamine in the contralateral RRF. When combined with large SDA lesions, A8 lesions impaired but did not eliminate mating. Thus the SDA-RRF pathway, but not an SDA-A8 pathway, is essential for sexual behavior in male gerbils.