The knowledge and practice of physicians and nurses with regard to immunization has been assessed. A self-administered questionnaire with 50 statements related to knowledge and practice of vaccination was distributed among workers in 50 MOH PHCs in Riyadh city. 506 questionnaires were returned, 479 were analysed. A response rate of almost 70%. For most of the statements cited a correct response of knowledge & practice was obtained from more than 80% of the sample. However for few others, correct response has dropped to 40% or less. Experience in dealing with vaccination, and a formal training in vaccination were not significantly associated with the responses of both physicians and nurses. Inspite of the limitations of this study it could be fairly concluded that the overall knowledge and practices of childhood immunizations among the primary care providers surveyed was good. Significant gaps still exist. This highlights the need for continuous training and supervision of health care providers dealing with children immunization.