Speech errors have been used in the construction of production models of the phonological and semantic components of language, and for a model of interactional processes. Errors also provide insight into how speakers plan discourse and syntactic structure,. Different types of discourse exhibit different types of error. The present data are taken from interviews concerned with domestic tasks, such as routines for preparing family dinners and dinner parties, getting the family off to work, the organization of a baby-sitting pool, and the layouts of apartments. There are almost no phonological errors, and few syntactic errors. The most common type of corrections are of semantic errors or errors of discourse ordering. Four major types of semantic errors are discussed: (1) semantic error involving the correction of potential ambiguity, if both interpretations would be plausible in the context; (2) the correction of the level of lexical specificity; (3) the correction of memory or fact; (4) the correction of the ordering of the discourse components, which provides crucial insights into the process of planning discourses. Cases not marked as errors by speakers, but which current syntactic models do not consider well-formed sentences are also discussed. (Author/CLK)