This document describes the biology of Lolium multiflorum Lam. (Italian ryegrass), Lolium perenne L. (perennial ryegrass) and Lolium arundinaceum Schreb. (tall fescue), with particular reference to the Australian environment, cultivation and use. Information included relates to the taxonomy and origins of cultivated L. multiflorum, L. perenne and L. arundinaceum, general descriptions of their morphology, reproductive biology, biochemistry, and biotic and abiotic interaction. This document also address the potential for gene transfer to occur to closely related species. The purpose of this document is to provide baseline information about the parent organism in risk assessment of genetically modified L. multiflorum, L. perenne and L. arundinaceum that may be released into the Australian environment.