The Left Index is designed to be a comprehensive source of information on leftist and radical media. The emphasis is on political, economic, social and culturally engaged scholarship inside and outside academia. A secondary emphasis is on significant but little known sources of news and ideas. Other topics covered include wars, the labor movement, ecology and environment, race and ethnicity, social and cultural theory, sociology, sexuality, art & aesthetics, philosophy, history, education, law, and globalization.

Historically significant early Left publications such as The People (est. NY 1891), and The Class Struggle (1931-1937), but there is limited coverage of The Daily Worker (1924-1958). Also indexed are classic texts by Marx, Lenin, Trotsky, Engels and others, written in the formative years of the Left, also are covered.