Despite substantial advances in family health and family planning over the past 30 years, global population has continued to grow by about 80 million people each year, with the total surpassing 6 billion people in 1999. Six Billion and Counting examines the consequences of continuing population growth for the world's resource systems and for national and global food security.

The authors offer a sober analysis of a complex and alarming situation. They assess the progress the world has made in controlling population growth and point to the areas where future difficulties will lie. They describe the effects of rapid population growth on social and economic conditions and on natural resources, and they consider what population growth will mean for the food security of poor people and poor countries. In addition, they address how sociocultural norms and the roles of women and children in traditional societies affect birth rates.

According to the authors, neither the population "pessimists," who predict that population growth will lead to a catastrophic exhaustion of natural resources, nor the population "optimists," who predict that technological advances can solve all of the problems raised by population growth, offer the most useful approach to this problem. Instead, Leisinger and his coauthors argue that new technologies mitigating the harmful effects of rapid population growth can give the world valuable time to take the complex and multifaceted steps needed to reduce population growth rates to sustainable levels.