The objective of this study was to examine the effects of variations in presentation of play materials on social behaviour of 18- to 30-month-old children. The study group included 102 children attending infant and toddler classes in 14 public childcare centres in Israel. Play materials were presented to the children either in a suggestive manner (as part of a scenario suggesting a context for play) or a random manner (without any planned organisation). Social behaviour of the two age groups was differentially affected by the manner in which play materials were presented. Toddlers showed a decline in aggressive behaviour following the suggestive presentation, whereas infants showed an increase in aggressive behaviour. Clinical implications of the current study include the possibility of using physical environmental variables as means for affecting children's experiences in childcare. (Contains 1 table and 3 figures.)