This paper examines farm and household characteristics associated with a rapid fertility decline in a forest frontier of the Ecuadorian Amazon. The Amazon basin and other rainforests in the tropics are among the last frontiers in the ongoing global fertility transition. The pace of this transition along agricultural frontiers will likely have major implications for future forest transitions, rural development, and ultimately urbanization in frontier areas. The study here is based upon data from a probability sample of 172 women who lived on the same farm in 1990 and 1999. These data are from perhaps the first region-wide longitudinal survey of fertility in an agricultural frontier. Descriptive analyses indicate that fertility has plummeted in the region, which is surprising since it had remained high and unchanging among migrant colonists up to 1990. Thus only half of the women in our sample reported having a birth during the 1990-1999 time period, and most women report in 1999 that they do not want to have any more children. Analyses, controlling for women's age, corroborate hypotheses about land-fertility relations. For example, women from households with a legal land title had fewer than half as many children as those from households without a title. Large cattle (pasture) holdings and hiring laborers to work on the farm (which may replace household labor) are both related to socio-economic status that is traditionally associated with lower fertility. Similarly, distance to the nearest community center is positively related to fertility. Factors negatively related to fertility include increasing temporary out-migration of adult men or women from the household, asset accumulation, and access to electricity.