Spontaneous speech errors provide valuable evidence not only for the processes that mediate between a communicative intention and the articulation of an utterance but also for the types of grammatical entities that are manipulated during production. This study proposes an analysis of speech errors that is informed by grammar theory. In particular, it is shown how characteristic properties of erroneous German utterances can be accounted for within Distributed Morphology (DM). The investigation focuses on two groups of errors: Errors that result from the manipulation of semantic and morphosyntactic features, and errors which appear to involve the application of a post-error repair strategy. It is argued that a production model which incorporates DM allows for a straightforward account of the attested, sometimes complex, error patterns. DM mechanisms, for instance, render unnecessary the assumption of repair processes. Besides providing an account for the attested error patterns, the theory also helps us in explaining why certain errors do not occur. In this sense, DM makes for a psychologically real model of grammar.