The objectives of this study were to determine (1) the proportion of physicians who do and do not recommend that children receive all available vaccines and (2) physician characteristics, attitudes, and behaviors associated with not recommending children receive all vaccines. A self-administered, cross-sectional electronic survey of physicians was conducted in 2005. Analyses were restricted to pediatricians (n = 250) and family practitioners (n = 484) who indicated they see at least five pediatric patients per week. A total of 1,935 surveys were distributed, and 1,251 (65%) physicians responded. Eleven percent of the physicians included in the analysis did not recommend to parents that children receive all available vaccines. Compared with physicians who recommended all vaccines for children, physicians who did not were more likely to be family practitioners versus pediatricians (OR = 2.9, CI = 1.4-5.8), agree or be neutral versus disagree that they have some concerns about childhood immunization safety (OR = 3.1, CI = 1.8-5.2), and have <or= 3 versus >or= 8 physicians in their practice (OR = 2.0, CI = 1.1-3.7). We conclude that physician characteristics and concerns about childhood immunizations are associated with not recommending all childhood vaccines. Further investigation of physicians' concerns about vaccine safety is needed to improve health communications directed toward health care providers.