In vitro mutagenesis of Dendrobium 'Earsakul' was carried out by incubating the protocorm-like bodies in 0-5 mM sodium azide for 1 h. Twenty-eight putative mutants were evaluated for genetic variability compared to untreated control plants using inter-simple sequence repeat (ISSR) analysis. Polymorphic fragments were produced by 9 of 12 ISSR primers. A total of 173 amplified ISSR fragments varying in size from 140 to 5000 bp were obtained, 39 of which were polymorphic (22.5%). Of the 28 putative mutants, 15 (53.6%) showed altered genetic profiles compared to control and were identified as mutants. These results suggest that sodium azide can be effectively utilized to generate mutants in Dendrobium 'Earsakul', and ISSR provides a powerful tool that allows efficient early detection of these mutants. The identified mutants are currently being multiplied for further evaluation of their horticultural characteristics.