This article examines the study of natural history on the imperial periphery in late colonial Spanish America. It considers the problems that afflicted peripheral naturalists-lack of books, instruments, scholarly companionship, and skilled technicians. It discusses how these deprivations impacted upon their self-confidence and credibility as men of science and it examines the strategies adopted by peripheral naturalists to boost their scientific credibility. The article argues that Spanish American savants, deprived of the most up-to-date books and sophisticated instruments, emphasised instead their sustained experience of local nature and their familiarity with indigenous knowledge. It details how some creole naturalists, such as the Mexican José Antonio Alzate, questioned the applicability of European classificatory systems to American fauna and flora, and it analyses the complex relationship between natural science and creole patriotism.