The practice of physical exercises under certain environmental conditions in carriers of sickle cell trait (SCT) may be associated with microvascular injury such as renal vasculary disease (1, 2, 3) . The increase in ambient temperature and high humidity seem to play a significant role in the occurrence of rhabdomyolysis reported post exercise in these individuals (2, 3). However, adequate fluid intake during exercise would limit the sickling process and therefore reduce the risk of microvascular injury (2). Our study assessed the effect of hydration ad libitum on thermoregulatory responses during two football matches in carriers of sickle cell trait in tropical climates. Twenty two students from the Higher National Institute of Popular Education and Sport (INSEPS) of Dakar, male, black, aged 26 ± 2.16 years and weighing 65 ± 5.45 kg, for a size of 1.75 ± 0.08 m, participated to the study. Eleven (11) subjects were genotype AA (control group) and 11 were of genotype AS (sickle cell trait: SCT). A hemoglobin electrophoresis led to the discovery of the presence of abnormal hemoglobin HbS of SCT carriers. Subjects were randomized into two teams: A team of 11 players consisting of 6 subjects AA and 5 SCT carriers, and a B team of 11 players, including six SCT and five AA. These teams competed in two football games separated by two weeks in comparable environmental conditions (temperature: 24.5 to 25 ° C, humidity: 65-68%). In the first game, only players of Team A could drink water freely without restriction during the match (6AA hydrated and 5SCT hydrated), while the players of Team B were not allowed to drink during the match (5AA no hydrated + 6SCT no hydrated). Conditions were reverse in the second match. Rectal temperature of subjects in both groups was taken before and after football matches with a thermometer. Body weight was assessed at rest and recovery in both groups. Our results showed that sickle cell trait is not a limiting factor in thermoregulation and that great hydration during physical exercise can significantly reduce the increase in rectal temperature and weight loss in both groups. Keywords: Sickle cell trait – Football match – Thermoregulation – Hydration