This new edition of the Baja California Plant Field Guide discusses or describes over 715 different plants in more than 350 genera in 111 families. Of these, approximately 32% are endemic to the region, 50% can also be found in southern California (e.g., San Diego County), and about 45% are new additions in this edition. In a field guide like this it is impossible to address all of the plant species in our region, but we have tried to compensate by discussing the overall diversity of the selected plant families and genera in introductory paragraphs preceding each species discussion. In this manner, we hope to give the reader a better understanding of the plant diversity that is not directly supplied by our book in photos and text.