BACKGROUND: Complementary and alternative medicine (CAM) refers to the use of nonconventional medical practices together with standard medical care. Specific forms of CAM included in this study are the use of honey, dry and wet Hijama, Quran, Zamzam water, Nigella sativa (black seed), and others. The objective was to determine the prevalence of the use of different CAM modalities by the attendees of primary health-care centers (PHCCs) and assess the reasons behind their use. MATERIALS AND METHODS: A cross-sectional study was conducted at PHCCs in the cities of Dammam and Al Khobar, over a period of 12 months. The study population was patients and their accompanying relatives attending the PHCCs, aged 18 years and above. Data were collected using a self-administered questionnaire in Arabic designed by the investigators after a review of the literature on the use of CAM. Questionnaire was modified after pilot testing among 200 medical students, and was validated by two expert consultants of the family and community medicine department at the university. The questionnaire was administered and supervised by the 3 rd and 4 th year medical students. Data were entered and analyzed using the SPSS version 16 (SPSS Inc., Chicago, IL, USA) statistical software. Descriptive statistics were computed, and odds ratios were calculated for associations between CAM use and various independent factors. Logistic regression analysis was used to determine the factors which predict the use of CAM by attendees. All the analyses were performed at α =0.05. RESULTS: The total number of attendees interviewed was 2114; 52.5% of whom reported using CAM. The types of CAM varied in their popularity of use, the majority of users favoring honey and Quran, 24.6% and 20.5%, respectively. Recommendations by relatives and friends were reported as the most common reason in this sample for using CAM (56.1%). Age, awareness of CAM, perceptions that use of CAM is better, use of CAM helps, herbs had no side effects, CAM was easy to obtain, and the attendee currently suffers from a disease were significantly associated with higher CAM use. CONCLUSION: More than 50% of the participants reported using CAM; honey and Quran were the most widely used modalities. For people to make informed decisions on the use of complementary medicine, physicians should impress on their patients to inform their doctors of their use of complementary medicine modalities so that encouragement could be given where appropriate.