Winter grown cotton in the west Kimberley (near Broome) has produced exceptionally high yields (>10 bales/ha) and premium quality fibre. Crops are irrigated daily, according to a formula based on &quote;crop factors&quote; and daily evaporation. However, the crop factors are estimates derived from other areas and may not represent efficient water use. Generally, crops near Broome have required 9 ML/ha applied water compared to about 6 ML/ha for similarly grown crops on drip irrigation at Katherine (NT). There is a clear need to accurately define the irrigation requirements of Bollgard II® cotton grown in a winter production system in the west Kimberley.