Purpose: To examine the role of linguistic input in how young, typically developing children use the 3rd person singular -"s" (3S) inflection. Method: Novel verbs were presented to 16 young children in either 3S contexts (e.g., "The tiger heens") or nonfinite (NF) contexts (e.g., "Will the tiger heen?"). The input was further manipulated for length such that half of the presentations in each context had adjectives modifying the subject. Children were then prompted to use the novel verbs in contexts requiring 3S and in contexts requiring an infinitive form. The children's use of 3S with familiar verbs was also examined. Results: Novel verbs heard only in 3S contexts were more likely to be produced with 3S in obligatory contexts and were more likely to be inappropriately applied to infinitive contexts than novel verbs heard only in NF contexts. Degree of 3S use in obligatory contexts was lower for familiar verbs than for novel verbs heard only in 3S contexts but higher than for novel verbs heard only in NF contexts. Length was not a significant factor. Conclusion: Linguistic input appears to have a strong effect on how young children use the 3S inflection in newly encountered verbs.