The stability of the factor structure of the California Critical Thinking Disposition Inventory was re-examined using a convenience sample of 800 undergraduate students from nursing (n = 520 first bachelors' and n = 185 second bachelors' students) and biology (n = 95) enrolled in introductory courses in their majors at a 4yr. mid-Atlantic public university. Ages ranged from 17 to 54 years (M = 23.0, SD = 5.9), with 92 men and 707 women (1 missing). 685 participants identified themselves as Euro-American, 65 as African American, 9 as Hispanic, 26 as Asian, and 11 as “Other” (4 missing). The inventory developed by Facione in 1994 is a 75-item, forced-choice, adjective checklist, yielding seven subscores and a total score assessing testees' disposition toward critical thinking. A principal components factor analysis did not replicate the original factor structure of seven factors but supported the stability of a four-factor structure which had emerged in previous work by Walsh and Hardy and by Kakai. When the 75 original items were reduced to 25, the explained variance for the inventory improved from 27% to 44.95%. Thus, further investigation and continued refinement is warranted.