When talented, motivated and highly trained athletes meet for competition the margin between victory and defeat is usually small. When everything else is equal, nutrition can make the difference between winning and losing. Although the primary concern of many athletes is to supplement the diet with protein, vitamins and minerals, and a range of more exotic compounds, key dietary issues are often neglected. Athletes must establish their nutritional goals, and must also be able to translate them into dietary strategies that will meet these goals. Athletes are often concerned with dietary manipulations in the period around competition, but the main role of nutrition may be to support consistent intensive training which will lead to improved performance. Meeting energy demand and maintaining body mass and body fat at appropriate levels are key goals. An adequate intake of carbohydrate is crucial for maintaining muscle glycogen stores during hard training, but the types of food and the timing of intake are also important. Protein ingestion may stimulate muscle protein synthesis in the post-exercise period, promoting the process of adaptation in the muscles. Restoration of fluid and electrolyte balance after exercise is essential. If energy intake is high and a varied diet is consumed, supplementation of the diet with vitamins and minerals is not warranted, unless a specific deficiency is identified. Specific strategies before competition may be necessary, but this requirement depends on the demands of the sport. Generally, it is important to ensure high pre-competition glycogen stores and to maintain fluid balance. There is limited evidence to support the use of dietary supplements, but some, including perhaps creatine and caffeine, may be beneficial.