We used data on 22,899 cancer cases collected by the New Mexico Tumor Registry to examine the relationship between patient age and the use of potentially curative therapy for cancers of selected sites and acute leukemias. For cancers of most sites, either local or regional stage, the proportion of cases receiving potentially curative therapy declined with age. For local-stage cancers, the proportion not given any treatment increased with age. Overall mortality rates during the first year after diagnosis were much higher for local-stage cases without treatment than for those who received treatment. These data show that cancer therapy varies with age and suggest that decision making regarding therapy is influenced by the presence of other diseases.