The origin of the pasture species grown in New Zealand and the development of ecotypes are briefly described. The effects of environmental factors such as rainfall, temperature, soil type, soil fertility, grazing pressure, and pests and diseases on plant breeding objectives and choice of species in different regions of the country are discussed. The value of incorporating plant material from Mediterranean sources into New Zealand-bred cultivars of ryegrass, white clover and Lotus is illustrated, but the importance of local plant collections in the development of cultivars such as Nui and Ellett ryegrass and a hill country white clover is also emphasized. The possibility of breeding cultivars specifically for overseas markets is discussed.