The article focuses on the omission of locative prepositions in child Russian. We report on two experiments: a production task and a comprehension task. Results from the elicited production task show that the majority of 2- and a minority of 3-year-olds (i) omit locative prepositions at nonnegligible rates, and (ii) do not conform to targetlike case-assignment patterns in utterances involving preposition omission. Findings from a sentence-picture matching task indicate that children who omit prepositions in production perform significantly worse on the comprehension task than children from the same age group who reliably produce locative prepositions. We suggest that these findings are in line with the hypothesis that preposition omission reflects a non-target-like underlying structure in children's grammar, which initially involves only one underspecified locative category.