Although the Black-headed Grosbeak (Pheucticus melanocephalus) is a common breeding bird in many parts of western North America, little is known about its breeding biology. Apart from a few anecdotal reports (Bent 1968), information on the breeding biology of this species comes from a single study performed in California (Weston 1947). The objective of the present study was to examine the breeding biology of a population of Black-headed Grosbeaks in northern Utah.