A study investigated children's difficulty in learning color words and attempted to determine whether the difficulty was perceptual, conceptual, or linguistic. The subjects were 24 two-year-olds, half with knowledge of color words and half without, and a similar control group. The experimental subjects were given conceptual and comprehension tasks for which the responses depended on color discrimination. In all cases, color was available as an inferential tool to the children who knew no color words, reducing the likelihood but not ruling out the possibility of a conceptual obstacle. However, children who knew color words appeared to do no better on the nonlinguistic color tasks than those without knowledge of color words. Possible explanations concern different kinds of linguistic or conceptual constraints at work. (MSE)