In this article, two accounts of the variable use of inflection in adult second language (L2) acquisition are examined. The Missing Surface Inflection Hypothesis (MSIH) proposes that L2 learners have unconscious knowledge of the functional projections and features underlying tense and agreement. However, learners sometimes have a problem with realization of surface morphology, such that they resort to non-finite forms (e.g. Haznedar and Schwartz, 1997; Prévost and White, 1999). The Impaired Representation Hypothesis (IRH) claims that L2 inflection is essentially impaired, due to lack of functional categories, features or feature strength (e.g. Eubank, 1993/94; Meisel, 1997). These views make different predictions for adult L2 acquisition. Spontaneous production data from two adult learners of French and two adult learners of German are examined. The data show that finite forms do not occur in non-finite contexts, that learners exhibit syntactic reflexes of finiteness and that inflected forms largely show accurate agreement. These results suggest that adult L2 learners represent finiteness and agreement at an abstract level, rather than being impaired in this domain, supporting the MSIH.