A study investigated the hypothesis that children learning Spanish as a first language learn rules for assigning stress, as opposed to simply memorizing stress for individual words. The subjects were 50 Spanish-speaking preschool children. In one portion of the experiment, they imitated sets of 2, 3, or 4 Spanish nonsense words that were segmentally identical but minimally contrasting in stress placement. The novel word sets contained regular/irregular stress contrasts in two- and three-syllable consonant- and vowel-final words and three prohibited stress types. In another portion of the experiment, spontaneous speech data containing a variety of word types were collected in an object-naming task. The imitation-task data clearly support the rule-learning hypothesis, and the spontaneous speech data support it somewhat less well. Results also suggest that the stress rule learning is essentially complete by age 3 because few age differences were found in the data. (MSE)