The problem with which this study is concerned is that of determining the relative differences in the job satisfaction of professional librarians employed in public, college/university, and special libraries. The purposes of the study were as follows: 1. To determine the differences in job satisfaction experienced by professional librarians working in public, college/university, and special libraries. 2. To determine if differences in job satisfaction are influenced by the factor of sex. 3. To determine if differences in job satisfaction are influenced by the factor of the size of the library staff. Statistically significant differences were found in job satisfaction between public and special librarians. Statistically significant differences were also found in the JDI Work scale between public and special librarians. Statistically significant differences were found on the JDI Pay and Work scales between female librarians and the females in the norms supplied by Patricia C. Smith. No statistically significant differences in job satisfaction were found associated with the size of the library staff or with sex. Females had higher scores on four of the five Job Descriptive Index scales than did males, but none of the differences were statistically significant.