With the objective of determining the best harvesting time for obtaining good quality fiber of three cultivars and eleven promising strains of cotton (Gossypium hirsutum L.), one experiment was conducted in Capinópolis-MG, during the 1981/82, 1982/83 and 1983/84 growing seasons. The fiber samples were taken at three different times: A - at 40% of open bolls; B - at 70% of open bolls; and C - at open top bolls. The samples were sent to the Instituto Agronômico de Campinas for technological characteristics determination. Results indicated that field weathering caused decrease on fiber index, uniformity and strength values for the three seasons. In 1981/82 and 1983/84, the best values were obtained at the first stage, with significant differences among genotypes for fiber percentage and index, uniformity, length and micronaire. In 1982/83, the best values for fiber percentage, length and micronaire were obtained at the B harvesting time. Genotype significant differences were determined for fiber index, length and uniformity. Strength was considered one of the most affected fiber characteristics by the harvesting time at the three years.