Reported is a study of the development of conservation and measurement concepts, with reference to certain task factors which may affect performance. A group of 129 first and second graders were given a test of conservation and measurement consisting of five problem types crossed with three transformation types. The problems all involved moving liquid from one of two identical containers into a container of a different shape. The dominance of perceptual versus numerical cues was varied by using clear and opaque containers, by measuring out the liquid using equal or unequal units, and by varying the order of the cues. The transformations were those making equal quantities appear unequal; those making unequal quantities appear equal; and those appearing to reverse the direction of inequality between two quantities. Achievement models were proposed and tested by multivariate analysis of variance. Results indicated that numerical cues were as significant as perceptual cues in most conservation problems; that measurement was meaningful to the majority of the children tested; and that order and equivalence problems were of equal difficulty. (MM)