With the purpose of determining the best vigor tests for cotton seeds, laboratory tests and a field experiment were made, using chemically delinted seeds of two cultivars, I AC 13-1 and IAC RM-3, stored in a dry chamber and under laboratory conditions. The following laboratory tests were performed: 1. percentage of emergence; 2. velocity of emergence - based on the number of plants emerged daily; 3 germination - being it's first counting as a vigor test; 4. rapid aging - the seeds were kept in the rapid aging chamber for 36, 48 60 and 72 hours; 5 ammonium chloride - the seeds were imerged in a 4% solution for 1,2 and 3 hours. Seed yield and the percentage and velocity of emergence were evaluated in the field experiment. The statistical analysis and interpretation of the results indicated that: the number of days required to make the last counting of the germination can be reduced; the first counting of this test was not efficient to determine the seed vigor; the best vigor test was obtained by keeping the seeds in the rapid aging chamber for 72 hours.