Interspecific hybridisation between tetraploid Lolium perenne L. (Lp) and L. multiflorum Lam. (Lm) was investigated by using morphological genetic markers. Fluorescent-root and awned-floret phenotypes are dominant in Italian ryegrass (L. multiflorum), so seed-parent Italian ryegrass plants were emasculated to eliminate the possibility of self-fertilisation. The percentages of germination were 84.3% in Lp x Lm and 90.6% in Lm x Lp crosses. The fluorescent seedlings were 81.8% in Lp x Lm and 83.7% in Lm x Lp crosses, and interspecific hybrids were 88.8 and 97.3%, respectively. The percentage of self-fertilisation was 4.0% in the perennial ryegrass. Pollen viability was 90.2% in the Lp x Lm and 91.0% in the reciprocal cross. The direction Lp x Lm seems to be a suitable method to produce interspecific hybrids on a mass scale.