The Santa Cruz Mountains, an area covering almost 1,400 square miles from San Francisco southward to the Monterey County line, are a part of the Coast Range of Central California. The Mountains and the adjacent lowlands have a rich vascular flora, and about 1,800 species, subspecies, varieties, forms, and hybrids of ferns, conifers, and flowering plants, distributed among 168 families, have been reported from the region. This comprehensive flora, the first of the area, is designed for use by both the serious beginner and the trained botanist. The flora is illustrated by 250 line drawing and ten photographs. In addition, there is a map of the Santa Cruz Mountains area and a stratigraphic profile of the rock formations. The stratigraphic profile and a section on geology have been contributed by Dr. Earl E. Brabb of the United States Geological Survey. Distributional notes, keys to families, genera, and species, pertinent synonymy, a glossary of technical terms, an index of place names, and common0name and scientific-name indexes form the body of the text. The Introduction contains a description of the geography of the Santa Cruz Mountains and adjacent lowlands, seconds on the geology and climate, a brief discussion and analysis of the vegetation and floristic affinities of the area, and a history of past botanical collecting. A selected list of references has been appended to allow the interested individual to pursue his studies further.