The authors describe an approach to adult intellect on the basis of content, unlike the traditional approach, which is mostly based on process. Thirty-two academic knowledge scales were rated by 202 college students, who also completed ability, vocational interest, and personality scales. Analyses of knowledge clusters and individual scales were used to evaluate commonality across ability constructs (verbal and spatial ability), vocational interests (realistic, investigative, and artistic), and personality (typical intellectual engagement and openness). The results support knowledge differentiation across fluid and crystallized abilities, show a pattern of positive correlations of arts and humanities knowledge with typical intellectual engagement and openness, and show correlations between math and physical sciences knowledge and realistic and investigative interests. Implications for the study of adult intelligence are discussed.