Successful immunization strategies depend on the provision of immunogenic vaccines and correct manufacture and storage of those vaccines. The aim of the present study was to assess the knowledge and practices of health workers dealing with immunization services about appropriate management of cold chain system. Their knowledge and practices concerning the surveillance activities of Adverse Events Following Immunizations [AEFIS] were also evaluated. A cross sectional study was conducted from June to September 2002 in all health offices providing immunization services in Alexandria. All health care personnel dealing with vaccines and cold chain present on the day of interview were included. The required data were collected through an observational checklist and two interviewing questionnaires. The results revealed that the total mean percent score of knowledge about vaccines and cold chain was only 49.50 % ± 9.73. The level of knowledge was related to the age, job, education of health worker and the more the better receiving training on cold chain system. The total mean percent practice score regarding cold chain system was 71.67%±9.2. The highest mean percent score [80.00 %±16.32] was obtained regarding elements of cold chain. As regards knowledge about surveillance of AEFIS, more than half of health workers [53.1 %] obtained poor knowledge score. The best knowledge was about adverse events following BCG immunization. Regarding practice, none of the visited sites had the special form for recording AEFIS, or the form for monthly recording of cases. It is concluded from the present study that the knowledge of health workers regarding immunization and cold chain is still low. The knowledge and practices regarding AEFIS is also poor. Extensive health education and training are needed to ensure that everyone involved in cold chain is familiar with all its facets. Provision of equipment like electric generators, solar refrigerators and cold chain monitors are considered important components for safe storage of vaccine and successful immunization program. Establishing a good surveillance system for AEFIS is recommended with development of rapid reporting channel from the field to the person in charge of monitoring vaccine- associated adverse events.