This study investigated different accounts of early argument structure acquisition and verb paradigm building through the detailed examination of the acquisition of the verb Go. Data from 11 children followed longitudinally between the ages of 2;0 and 3;0 were examined. Children's uses of the different forms of Go were compared with respect to syntactic structure and the semantics encoded. The data are compatible with the suggestion that the children were not operating with a single verb representation that differentiated between different forms of Go but rather that their knowledge of the relationship between the different forms of Go varied depending on the structure produced and the meaning encoded. However, a good predictor of the children's use of different forms of Go in particular structures and to express particular meanings was the frequency of use of those structures and meanings with particular forms of Go in the input. The implications of these findings for theories of syntactic category formation and abstract rule-based descriptions of grammar are discussed.