The study examined the association of attitudes with gains in knowledge for teachers who participated in a professional development project on literacy. First-grade teachers from 38 schools participated. The schools were randomly assigned to one of two conditions, with all teachers within a school assigned to the same condition. Each group received a two-day summer workshop prior to participating, followed by monthly workshops throughout the school year. The first cohort, the In-Class Mentor group, received additional weekly in-class support from mentors and participated for two years. The second cohort, the Regular Mentor group, did not receive extra support and only participated for one year. Pre- and post-assessments of participants on both a Teacher Attitude Survey, developed for this project, and on a Teacher Literacy Knowledge Survey documented significant increases in teachers' self-esteem regarding ability to teach reading, as well as in their literacy knowledge. Likewise, both groups of teachers felt positively about the professional development and became more positive by the end. Higher levels of resistance to professional development and to the ideology of the professional development were associated with smaller gains in knowledge for both cohorts. Yet, increased support for the teachers in the In-Class Mentor cohort was related to greater reduction in both barriers. Correspondingly, teachers in the In-Class Mentor group had a significant reduction in opposition to the ideology of the program and gained significantly more knowledge of reading concepts. Prior knowledge of the topic areas of professional development accounted for less variance in final knowledge for teachers in the In-Class Mentor group. Further, continued intensive support over a two year period for the In-Class Mentor cohort lead to additional gains in knowledge, increases in the corresponding areas of self-efficacy, and increments in teachers' feelings of support and satisfaction. In sum, attitudes of teachers were associated in a number of ways with the extent of gains in knowledge acquired from a literacy professional development program. In addition, comparison of two levels of intensity of the professional development indicated greater gains in knowledge, and associated changes in attitudes, for teachers in the more intensive version.