Using a newspaper article about a ceremony marking the retirement of baseball player Tom Seaver's uniform number, a study examined: (1) the effects of knowledge of baseball in general and of the career of Tom Seaver in particular; and (2) the effects of knowledge of word meanings in general and of words used in the passage specifically on 10th graders' recall of different aspects of passage content. Subjects, 159 10th graders from Illinois and Long Island, read a target passage and then were assessed on baseball knowledge and vocabulary knowledge. Vocabulary knowledge tended to affect the number of units recalled overall, whereas prior knowledge influenced which units were recalled. Prior topic knowledge influenced whether subjects produced a "gist" statement in their recall and how well they recalled numbers relevant to Seaver's career. High-knowledge subjects also tended to focus more on information given about Seaver's career than did low-knowledge subjects. Specific and general domain knowledge were so closely related that their effects could not be disentangled. A qualitative analysis of the protocols confirmed the general trends in the quantitative analysis. Results suggest both that domain knowledge and vocabulary have independent effects on comprehension and that these effects are on what is comprehended as well as on how much is comprehended. (Three tables of data are included; 20 references and 2 appendixes containing the reading selection and baseball terminology are attached.) (Author/KEH)