The approach was to use the Whole Farm Model (WFM) and Taranaki climate to compare a conventional, twice-a-day milking farm system with variations of once-a-day (OAD) milking and high-input systems. The aim was to compare production, return on assets (ROA) and risk as affected by climate and price variability. Simulations were run over 9 different climate years (1995/1996 - 2003/2004). The high-input system had the highest production (1333 kg milksolids (MS)/ ha) and highest ROA (10.8%), with variability thereof dampened by a feed buffer of higher quantity and quality that existed because of higher pasture yields (15.8 t dry matter (DM)/ha with 200 kg nitrogen (N)/ha vs. 13.5 t DM/ha with 105 kg N/ha for the other two systems), maize silage and grazing-off. The high-input system was followed by the OAD and conventional systems in terms of production (1068 and 975 kg MS/ha respectively) and ROA (9.8% and 9.2% respectively). Both OAD and conventional systems showed risk values nominally lower than high-input, but both these systems were more severely affected by climatic var iability, which lowered the average return and increased the risk relative to the return. Keywords: climate var iability, high input farming, once-a-day milking, return on assets