Visual stimuli can serve as positive or negative reinforcer for primates even if those stimuli are not accompanied with fluid reward or aversive punishment. Especially, social stimuli that are visually presented attract much interest of primates. Striatal neurons which receive strong projection of midbrain dopamine neurons have been reported to show predictive response of fluid reward. The striatum, especially in the ventral part, also receives neural projection from the brain areas that process social information such as the amygdala. Thus, it is possible that visual stimuli that convey social information also affect the activity of the striatal neurons. In this study, to elucidate the involvement of the striatum in social information processing, we recorded the activity of the monkey ventral striatal neurons while an arbitrary geometric pattern was associated with one of the visual images belonging to several categories such as the opposite sex, a face showing negative emotion, or foods. The precedent geometric patterns and the following visual images were separated by a brief delay period. Behavioral data showed the subject monkey's preference for the visual stimuli of the opposite sex and foods. Thirty two of 116 neurons recorded from the ventral striatum of a macaque monkey showed excitatory responses in relation to at least one of geometric pattern that becomes predictor of the following visual stimuli. Cluster analysis showed that the activity of the striatum neurons clearly discriminated the category of the visual stimuli. Moreover, the population activity was the highest in response to the socially preferable stimuli. To estimate how well individual neurons discriminate social stimulus categories, we computed the temporal change of ROC value in 32 excitatory responsive neurons by comparing neural activity between socially preferable and unpreferable stimuli. Results showed that ROC value increased while the geometric patterns that predicted the socially preferable stimuli were presented. These results indicate that the monkey ventral striatal neurons are involved in prediction of the visual image of preferable social information.