This working paper presents various population projections which explain the apparent difference between the 35-37% decline in birth rates in Java and Bali and 10% in the other islands since 1970 announced by the National Family Planning Board in 1980 and the preliminary results of the 1980 census. The 1980 census revealed an estimated population of 147,383,000 or 145,684,000 when Irian Jaya and East Timor are excluded. This is an intercensal increase of 27,467,000 or 2.32% over the same area since 1971 as compared with a growth rate of 2.05% between 1961-1971. This apparent discrepancy may be partly explained by different patterns of declining fertility and declining mortaltiy. Calculations from previous censuses and 1976 survey data indicate that total fertility rates fell from 5.6 in 1907-70 to 5.2 in 1971-75 to 4.9 in 1975. Mortality has also declined. Life expectancy is estimated to have increased from 42.5 in 1960 to about 46 in 1971 to 50 in 1976 and by an additional 2.5 years. Although none of the 120 projections of natural growth rates produces a growth rate as high as 2.32, other factors such as inaccuracies in age reporting (which would affect age specific fertility rates calculated by the own child method) and an undercount of 4-6% in the 1971 census compared with 2-4% in 1980 may also be involved.