Due the difficulties at the interpretation of the standard germination test of cotton seeds, this study was made to certify the influence of the substratum and the treatment at germination of the cultivar IAC-20 seeds. Three trials were made, the first at Iaboratory, constituded by the standard germination test using as substratum cloth, newspaper and germitest paper; the second trial at vegetation-house, used as substratum sand, soil and a mixture composed by soil-sand-organic material. Both trials were made with seeds treated by Thiabendazole (400g/100kg of seeds) and with seeds without any treatment. The third trial was constituted by the sanity test, having as objective to determinate the pathogens of the seeds and the iniluence of the application of fungicide Thiabendazole and Captan. The results showed a high incidence of fungus at the seeds and the treatments efficacy. The worst substratum used at lab, was the newspaper; and the best substratum used at vegetation-house was sand.