dietary supplement is defined as a product taken orally that contains a "dietary ingredient" (vitamins, minerals, herbs, amino acids, enzymes, etc.), and is intended to supplement one's diet. Dietary supplements include plant extracts and concentrates from foods. Supplements help provide required nutrients to fulfill nutritional levels for daily training or competitive performance, and can help remedy nutritional deficiencies. Therefore, it is important that sports professionals have a thorough knowledge of these supplement products. However, athletes need to be informed about the use and possible benefits, side effects, and risks associated with the use of dietary supplements. Four objectives guided this study: (a) assess the use and attitudes of professional athletes in Saudi Arabia toward dietary supplements, (b) determine the availability of dietary supplements in Saudi Arabian markets, (c) identify the microbiological quality and safety of dietary supplements in Saudi Arabia, and (d) evaluate the impact of educational program on the knowledge and attitude of professional athletes in Saudi Arabia toward dietary supplements. In order to achieve the first objective, approximately 105 professional athletes were recruited as subjects from three different Saudi Arabian sports clubs. A questionnaire was designed to determine factors that influence professional athletes' choices and use of dietary supplements. To achieve the second objective, twelve stores from each region of Riyadh were selected to assess the availability of dietary supplements on the market. In the third objective, approximately 80 different supplements from Riyadh were analyzed for microbial quality and product safety. The aim of the fourth objective was to develop a program to educate professional athletes in Saudi Arabia about the benefits of dietary supplements. Both pre- and post-assessments were used. The majority of athletes indicated that their use of supplements was for the purpose of improving health and performance. The availability of different supplements ranged from approximately 23 to 97% according to the demand. In addition, of 80 most popular supplements selected for microbiology analysis, nine were shown to have contamination. Thus, this study provides a better understanding of factors that influence the attitudes of professional athletes with regard to the use of dietary supplements. The study identifies dietary supplements available in the Saudi Arabian market, and more importantly provides analyses to differentiate the quality among these products. The overall effect of this research is that professional athletes in Saudi Arabia and athletes worldwide will be able to make informed decisions about their choices and use of dietary supplements.