The Agreement/Tense Omission Model (ATOM) predicts that English-speaking children will show similar patterns of provision across different tense-marking morphemes (Rice, Wexler & Hershberger, 1998). The aim of the present study was to test this prediction by examining provision rates for third person singular present tense and first and third person singular forms of copula BE and auxiliary BE in longitudinal data from eleven English-speaking children between the ages of 1;10 and 3;0. The results show, first, that there were systematic differences in the provision rates of the different morphemes; second, that there were systematic differences in the rate at which all of the three morphemes were provided with pronominal and lexical subjects; and, third, that there were systematic differences in the rate at which copula BE and auxiliary BE were provided with the third person singular pronominal subjects It and He and the first person singular subject pronoun I. These results replicate those of Wilson (2003), while controlling for some possible objections to Wilson's analysis. They thus provide further evidence against the generativist view that children's rates of provision of different tense-marking morphemes are determined by a single underlying factor, and are consistent with the constructivist view that children's rates of provision reflect the gradual accumulation of knowledge about tense marking, with much of children's early knowledge being embedded in lexically specific constructions. © 2008 Cambridge University Press.