Historical studies of science in Spanish America emphasize efforts by local groups to overcome adverse conditions, participate in international networks of knowledge, and promote science as essential to national projects of development. Initially, research groups were small, fragile, and dominated by individual pioneering figures. Many members were astute and creative in overcoming inadequate funds, libraries, and laboratories, and in surviving as researchers in societies that usually placed a low cultural value on science. This chapter will describe the main scientific events, characters, and trends in Spanish South America between the late eighteenth century and the late twentieth century. The emphasis will be in the life and exact sciences and in their connection to medicine and engineering.