The aim of the Kangaroo research project was to enhance the well-being of children under three years of age in Finnish day-care centres. In this experimental intervention study adults were encouraged to take a more sensitive and active role especially during "free play." In six Kangaroo groups and five control groups adults (N = 28) and children (N = 38) were observed during three mornings in the autumn and in the spring in order to explore the impact of the Kangaroo intervention. The results indicate that it was possible to increase the adults' sensitivity and enhance their activation skills through the Kangaroo intervention when the starting level of professional qualifications and motivation was sufficiently high. There were also significant differences in quality within both the Kangaroo groups and the control groups. Between individual adults the differences were at a maximum and quality was found to be unstable even when the staff was the same. (Contains 6 notes and 6 figures.)