Chemical-mutagen treatment of Ethiopian mustard (Brassica carinata A. Braun) line C-101 seeds (which contained about 441 g/kg C22[ratio ]1) led to isolation of a mutant, L-935, which contained about 190 g/kg erucic acid (intermediate C22[ratio ]1) in the seed oil. The objective was to determine the inheritance of the intermediate C22[ratio ]1 level in this mutant. The mutant L-935 was reciprocally crossed to C-101 and to the mutant line L-2890 (which contained 112 g/kg C22[ratio ]1; low). The F1, F2 and BC1F1 generations were obtained. Cytoplasmic effects were not observed in any of the crosses. The analysis of the fatty acid composition in the F2 populations from the crosses of L-935 with C-101 revealed a segregation pattern fitting a ratio 1[ratio ]2[ratio ]1 for intermediate, high and very high C22[ratio ]1 content. The segregation patterns fitted a one-locus (designated M2) model with two alleles (M2 and mi) and with partial dominance of high over intermediate C22[ratio ]1 content. The segregating generations of the crosses L-935×L-2890 showed a strong transgressive segregation with C22[ratio ]1 values ranged from 1·3–406·5 g/kg. The analyses of the F2, BC1F1 and F3 generations indicated that the combination of alleles at two loci, M1 and M2 controlled the transgressive segregation for C22[ratio ]1 content. The proposed genotypes (C22[ratio ]1 content) for each parent were as follows: L-935 (190 g/kg 22[ratio ]1)=MMmimiEEEE; L-2890 (112 g/kg C22[ratio ]1)=mmmmEEEE; and C-101 (441 g/kg C22[ratio ]1)=MMMMEEEE.