We use a decomposition model to analyze changes Of CO2 emission intensity in the developed countries for 1980-94. During this period, emission intensifies decreased by 33.26% from 788.7 u (1 u = 1 kg Of CO2/1000 US$ at 1990 prices) in 1980 to 591.9 u in 1994. The rate of decrease in CO2 emission intensifies has decelerated; the decrease during the first 7-year period was twice as fast as during the second period. A decrease in energy intensity accounted for about 70% of the total, with the remaining 30% attributable to fuel switching. This trend has changed recently, but the change is not significant.