The wet paddy yields in the states o f Peninsular Malaysia during the 19 75176 main and 1976 off seasons were studied in relation to changes in rainfall, dry spells, sunshine, maximum and minimum temperatures through the principles o f system approach. The main climatic factors influencing the yields were identified as rainfall during the 2nd to 5th months before harvest, the mean minimum temperature o f the 4th month before harvest and the mean maximum temperature o f the month before harvest, accounting for 83.92% o f the variations in the wet paddy yields. The various states o f Peninsular Malaysia had consistent differences in wet paddy yields since 1946 to through 1977 and these regional differences in yields appeared principally due to the climatic changes in rainfall and air temperatures.