This work examines three- to six-year-old children’s acquisition of the Spanishpassive. This structure, a notoriously difficult concept for early learners, exhibits great variationin age of acquisition cross-linguistically. Spanish, with two passive constructions, is an ideal casestudy for the role of frequency in the development of the passive. This study utilizes data fromCHIEDE, a spontaneous oral corpus spanning more than 20,000 words of child speech. Only alimited number of studies examining the passive have utilized spontaneous corpus data; as aresult, it is unclear if lexical semantic patterns are due to experimental or task effect - an issuethat only the inclusion of natural data can resolve. Results show that children only produce oneof two possible forms of the Spanish passive. Their production is also limited to action verbs.Finally, while children as young as 3;0 produce the passive, cross-sectional data show thebeginnings of a downward U-shaped developmental pattern. These results are explained in termsof acquisition by analogy as children utilize previously-acquired structures to create abstractsyntactic representations.