By the age of 3 children spontaneously produce agreeing third person singular and plural verbal forms, which they reportedly don’t comprehend until the age of 5 (Johnson, de Villiers, & Seymour, 2005 for English; Pérez-Leroux, 2005 for Spanish). This has been attributed to the un-interpretable nature of the number features involved. I present two sets of experimental evidence in children ranging from 14 months to ~5 years of age, depending on the language (French, Spanish). The first set of results from preferential looking and pointing tasks reveals that comprehension is not universally late. Miscomprehension, when present, is best characterized as relative mis-perception of agreement markers. The second set of experimental evidence pertains to very early sensitivity to (un-)grammaticality of French Subject-Verb agreement dependencies in preverbal children, as well as their changing preferences for (un-)grammatical stimuli over the course of 10 months (from 14 to 24 months of age). I propose to interpret these changes as evidence for young children’s maturing agreement representations, from surface phonological dependencies to abstract morphological features of the dependencies. Overall, young children’s knowledge of Subject-Verb agreement is abstract and productive by the time they spontaneously produce any verbal forms.