The influence of the granulometry of a gold pyrite concentrate and of the temperature during the biooxidation was studied as a pretreatment to increase the recovery percentage of gold by cyanidation of a refractory mineral from the mining company "Rio Chicama", which increased from 5.62% up to 28.33%. The sample consisted of 40.5 kg of gold pyrite concentrate, with the presence of arsenic called refractory mineral, from the Rio Chicama de Sayapullo mining company, which underwent 27 tests, which were screened at 80% through the sizes of 37; 53 and 74 μm ,, and subjected to three biooxidation temperatures 25; 45 and 65 ° C; making use of two replicas for each test, obtaining results that were used to make the metallurgical balance, and later the percentage of recovery of gold was calculated. The results show that, the maximum gold recoveries obtained are: 27.31% when the particle size i...