The article examines the long-term changes and the age homogamy of marriages that took place in the Czech Republic between 1920 and 2000. The analysis of data acquired from a study of vital registration is divided into a descriptive part – describing the age structure of the marriage market and the absolute degree of age homogamy – and an exploratory part – creating a log-linear model of the structure and changes of relative age homogamy. Three hypotheses are formulated in connection with the latter part of the analysis, of which the hypothesis about increasing age homogamy seems acceptable. Results from the descriptive analysis and the models show that age homogamy has been increasing during the 20th century, both in the case of first marriages and remarriages. The hypothesis about the greater degree of age heterogamy in the case of remarriages can also be accepted, while the testing of the third hypothesis, that the older the marital partners are the more heterogamous their age structure, proved inconclusive and requires further investigation.