This study investigated different accounts of children's acquisition of non-subject wh-questions. Questions using each of 4 wh-words ("what," "who," "how" and "why"), and 3 auxiliaries (BE, DO and CAN) in 3sg and 3pl form were elicited from 28 children aged 3;6-4;6. Rates of non-inversion error ("Who she is hitting?") were found not to differ by wh-word, auxiliary or number alone, but by lexical auxiliary subtype and by wh-word+lexical auxiliary combination. This finding counts against simple rule-based accounts of question acquisition that include no role for the lexical subtype of the auxiliary, and suggests that children may initially acquire wh-word+lexical auxiliary combinations from the input. For DO questions, auxiliary-doubling errors ("What does she does like?") were also observed, although previous research has found that such errors are virtually non-existent for positive questions. Possible reasons for this discrepancy are discussed. [This research was funded by Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany and by an ESRC Postdoctoral Fellowship.]