Monitoring an athlete’s immune function is a vital part of preparation for competition but current methods are limited in their ability to predict or detect early infection, fatigue and over-training. The ABEL®-sport test offers an exciting alternative. The test is a luminometric examination of the kinetics and intensity of the response of the NADPH oxidase, of capillary blood leucocytes after challenged in vitro with a receptor activator to produce reactive oxygen species (ROS). The reaction of ROS with the bioluminescent protein Pholasin^® leads to emitted light. The course of light production is followed and charted using the portable field luminometer, ABEL®-metre-1, over a 6 min period. Curves of light emission against time, compared to a standard reference, are used in the analysis of the results. Eleven elite cyclists were tested before and after 3 consecutive days cycling and in the morning of the 4^th day as part of a 4 day cycling training camp. The 77 results were classified into 5 distinct abnormal shaped curves and the reference shape. A strong positive correlation (r = 0.729, p < 0.05) was found between the frequency of occurrence of particular abnormally shaped curves and the severity of URTI symptoms two weeks post-camp. Frequency of abnormal shaped curves explained 63% variance in URTI symptoms (p < 0.05). Abnormally high light response curves of different intensities, recorded at the end of each day’s cycling indicated intense inflammation and possible incipient infection. The mornings after intense cycling provided objective evidence of recovery or fatigue. The morning results on day 4 identified 7 riders with major fatigue, 3 with mild fatigue and 1 normal. The ABEL®-sport test is admirably suited to twice daily monitoring during a training camp and the results of the test can be used to modify training regimens. Furthermore the results of our tests have accurately predicted the occurrence and severity of URTI symptoms two weeks post-camp.