Victor Raskin's taxonomy of knowledge, based on semantics theory, is adapted and applied to composition in English as a Second Language (ESL). Raskin's classification of knowledge as linguistic and encyclopedic is converted to a continuum from textual to extra-contextual, with contextual knowledge situated between the two. Textual knowledge is that relevant to understanding of grammatical aspects of the language; contextual knowledge means the awareness of inter-sentential relationships and the cumulative impact of all preceding text on cohesion and coherence; and extra-contextual knowledge refers to the elements that exceed lexical definitions, sentential rules, and compositional principles. In ESL composition, the last category of knowledge is about the American people, their social structures, cultures, expectations, values, behaviors, and language use. One ESL student's paragraph-long writing assignment is used to illustrate the three knowledge types. It is concluded that this approach provides some assistance in classifying, examining, and remedying problems commonly found in ESL composition, particularly as students from some cultures and educational backgrounds may be expected to have more or less knowledge in each area. It is emphasized that the three categories of knowledge are not distinct but exist on a continuum. A brief bibliography is included. (MSE)