Developmental changes in the expression of contrast in child discourse were investigated. Contrast is defined as a psychological phenomenon and applied to the domain of discourse topics. The development of the ability to produce utterances that are topically related to the previous conversational turn is considered. Four types and three levels of expression of contrast are identified. The four types of expression of contrast are (1) comparison between two states, (2) denial of a previously asserted state, (3) substitution of one item for a previously mentioned item, and (4) challenge of an implicit suggestion. Three levels of expressing contrast are taking issue with the explicit content of a previous speech, challenging an implicit suggestion, and challenging the appropriateness of a previous speech. Twenty hours of videotaped interactions involving four children from the ages of two to five and containing 450 expressions of contrast were analyzed. Four developmental phases were identified that progressed from explicit expressions based on the immediately preceding linguistic context to expressions of contrast based on more implicit or hypothetical concerns. Numerous examples are presented. (RW)