The chlorophyll mutations were investigated in a population of established cultivars of horsegram namely, HPKC-2 and VLG-1 induced through chemical mutagen ethyl methane sulphonate (0.1%, 0.2% and 0.3%).The usefulness of mutagens in mutation breeding depends not only on its mutagenic effectiveness but also mutagenic efficiency. Effectiveness denotes the frequency of mutations induced by a unit mutagen dose while efficiency is the measure of the proportion of mutation in relation to undesirable changes like injury, survival, meiotic aberrations. One thousand dry and genetically pure seeds of two horsegram varieties viz., HPKC-2 and VLG-1 were treated with three doses each of ethyl methane sulphonate having different concentrations viz., 0.1%, 0.2%, and 0.3%, to study the frequency and spectrum of induced chlorophyll mutations in HPKC-2 almost double the VLG-1. Four kinds of chlorophyll mutations in order of frequency of their occurrence viz., Chlorina Xantha Viridis Albina were observed due to mutagen (Ethyl methane sulphonate). 02% concentration of ethyl methane sulphonate produced maximum chlorophyll mutants (810) in variety HPKC-2 whereas in VLG1 0.1% (319) Overall maximum mutants were observed in the variety HPKC-2(1658). Maximum xantha types of chlorophyll mutants were observed in both the variety 330 (HPKC2) and 152(VLG1). Mutagenic effectiveness and efficiency were higher at moderate dose (0.2%). Based on the reduction in plant survival, germination, shoot length and seed fertility, ethyl methane sulphonate was found 1.70, 1.71, 1.23 and 1.33 times more efficient in VLG-1 than HPKC-2 while on the basis of root length ethyl methane sulphonate was found to be similar in both the varieties.