A study examined the type of Wh question (those introduced by who, what, when, where, why, or how) and the phrase structure rules required for the verb phrase to determine how they relate to the acquisition and development of the Wh question transformation. Children ranging in age from 2 to 6 years were given three tasks, each containing 36 stimulus sentences employed to measure competence in three areas of the Wh question transformation: imitation, comprehension, and production. Analysis showed that children's comprehension of who, what, where, and how questions was significantly better than their production of these questions because concrete referents were more readily available for these four types. The means for the various age groups for imitation and production revealed imitation was higher than production or not different from production for all age groups. The figures also suggested that although Wh questions containing the verb phrase present + do + verb were grammatically more complex than those containing the other two verb phrase types, the children did not have less facility with Wh questions containing present + do + verb, and, in fact, performed better with this type than with the other two. On imitation, most of the children were performing the operations of preposing and transposing, but as indicated by some of the responses, some of them did not apply the number agreement rule. The substantially larger number of deviant responses for production than for imitation suggests that children imitate Wh questions before they search for the semantic understanding needed to produce them. (HOD)