This study was conducted to investigate the effect of pre-weaning social contacts on social behaviour in a new herd formed three months after weaning, using four groups of twin kids of Tokara goats. During the three months of suckling period, each group formed twin kids and their mother was penned separately, except when the four kids selected from each of the four groups of twins were joined to experience social contacts for two hours once a week during the seven weeks. For another three months after weaning, the four kids experienced social contacts were kept together but isolated from the other group of four kids inexperienced pre-weaning social contacts. Then, all the eight kids were joined to form a new herd to observe the frequencies of butting and mounting between kids on the first two days, and the frequencies of the nearest neighbouring between kids in every thirty minutes on the third, fifth and seventh days. The behavioural data collected from the four kids experienced pre-weaning social contacts (E) were classified into three categories according to the social relationships between kids. They were twin relationship (a), cohabituating relationship during the three months after weaning (b) and unfamiliar relationship (c). The same classification was applied to the other four kids inexperienced pre-weaning social contacts (I). All the collected data were analyzed using χ^2 test and dual scaling method. The results obtained were as follows: 1. Kids (E) and kids (I) showed a similar tendency in butting, less frequently against kids (b) but more frequently against kids (c). 2. Kids (E) showed much higher frequencies of mounting than kids (I) and this was due to a difference in mounting kids (c). 3. Both kids (E) and kids (I) showed the nearest neighbouring more frequently to kids (B) but less frequently to kids (a) and kids (c) 4. The analysis of social behaviour using dual scaling method indicated that kids (I) showed much interest to butting kids (c) comparing with kids (E). Both kids (E) and kids (I) regarded kids (b) as more familiar neighbours than kids (a) It was suggested that pre-weaning social contacts tended to promote the social activities.