Chloroplast counts were made from the stomatal guard cells in haploid (n — 2x — 26) and in natural tetraploid (2n = 4x — 52) plants of Gossypium hirsutum L. and G. barbadense L. The mean chloroplast number was 10.46 ± 2.18 for haploids and 21.00 ± 3.31 for tetraploids.  The means from haploid plants did not overlap with the means from tetraploid plants in 280 plants evaluated. Cotton plants can be classified much easier and quicker from the cotyledon stage to maturity as haploids or tetraploids and as accurately as by chromosome counts.