T he associative strength between target and associates, a factor assumed to be critical but generally not controlled, and the type of conceptual relation (thematic and taxonomic) were manipulated independently in a matching to sample task to determine their respective effects on the matching behaviour of 4- and 6-year-old children. Perceptual similarity between target and associates was controlled and maintained at a low level. A preliminary task was designed to assess the associative strength between targets and several associated pictures. These judgments served to construct for each child the sets of stimuli used in the matching task. Exp. 1 opposed a strong and a weak associate with the target in different configurations: the sets included a target and two thematic associates, two taxonomic associates or one associate of each type. Children were asked to choose the picture that ''went well'' with the target. Data revealed the role of associative strength on matching choices. This factor interacted sometimes with the greater availability of thematic relations in 4- and 6-year-old children. In Exp. 2, two other configurations were tested. Thematic and taxonomic associates were both either strongly or weakly related with the target. Results replicated those of Exp. 1 and extended them. They showed that younger children were biased towards thematic relations only when these relations corresponded to strong associations. Thus, increasing experience with objects appears to reinforce both associative strength and thematic orientation. Finally, in Exp. 3, instructions orienting toward taxonomic choices modified responses in 6-year-olds only. Altogether, these results show the influence of specific instances and suggest that preschoolers' matching decisions are partly stimulus driven.