In a child day-care setting, the naturally occurring social-emotional behaviours and play interaction of 51 infants were observed and recorded. Individual differences in gender, age, temperament, and maternal parenting behaviours were examined to understand how these variables might be related to social-emotional adjustment of infants. The measures used in this study were Social-emotional Behaviour, Play Interaction, Temperament, and Parenting Behaviour. Results indicate that boys showed externalizing problem behaviours more than girls, and the 2-year-olds showed more internalizing problem behaviours such as withdrawal/separation than 1-year-olds. Additionally, adaptability of infants showed a negative correlation with externalizing problem behaviours. Maternal behaviours of over-protectiveness/permissiveness had relations with a low social capability and refusal/neglect had relations with high externalizing problem behaviours. The results suggest that individual differences in social-emotional adjustment are variously determined. (Contains 6 tables.)