The onset of maternal responsiveness by virgin female rats to foster pups was observed after (i) complete vomeronasal nerve cuts, (ii) partial olfactory bulb cuts, or (iii) the combined procedures. Although both vomeronasal nerve cuts and olfactory bulb cuts resulted in a more rapid onset of maternal care, relative to control animals with sham operations, animals sustaining the loss of both sources of olfactory input exhibited the shortest response latency. These findings are discussed in terms of the probable distinct functions of the two olfactory systems in the control of maternal behavior in the rat.