Book excerpt: Gender-Structured Population Modeling gives a unified presentation of and mathematical framework for modeling population growth by couple formation. It provides an overview of both past and present modeling results. The authors focus on pair formation (marriage) and two-sex models with different forms of the marriage function -- the basis of couple formation -- and discuss which of these forms might make a better choice for a particular population (the United States). The book also provides results on model analysis, gives an up-to-date review of mathematical demography, discusses numerical methods, and puts deterministic modeling of human populations into historical perspective.