For centuries sports are providing people entertainment and physical fitness. Often sports go hand in hand with competition. Olympic Games are organized every two years and the whole world is watching it. A crucial part of the competition is sports timing. A lot of people do sports and sport events take place on a large scale. Mass sport events attract over more than hundred thousand people and they all want accurate sport timing. This thesis focuses on analyzing the UHF RFID system used for mass sports timing, e.g. marathons. As of today UHF systems are commonly used in other industries, but are not optimized for sports timing. The main advantage of the UHF RFID system is the low cost of the individuals RFID tags used. Mass sporting events on a grand scale have contributed to the popularity of the UHF RFID systems. However, there are several sports timing specific challenges. Four major challenges can be identified: throughput, accuracy, missing detections and multiple antennas. There are several relationships between these challenges, e.g. there is a trade-off between accuracy and throughput. Optimized for throughput the system would attempt to read as many unique tags as possible, decreasing the probability of missing an athlete. In this situation the number of ’hits’ (the number of times an athlete is seen by the system while crossing a timing line) is low, making it difficult to record the precise starting or finishing time. An optimized reader algorithm is proposed. The algorithm dynamically finds a good balance between throughput and accuracy. As a result, the optimized reader algorithm switches faster to the next antenna and misses fewer athletes. Simulations of marathon races show that the proposed optimized reader is more efficient, has more hits and misses fewer athletes than the currently used standard UHF RFID reader.