This selection of Adams' work in two volumes brings together all his major research contributions. They are organized by subject matter rather than in strict chronological order. The first volume contains papers on the cobar construction, the Adams spectral sequence, higher order cohomology operations, and the Hopf invariant one problem, applications of K-theory, generalized homology and cohomology theories. The second volume is mainly concerned with Adams' contributions to characteristic classes and calculations in K-theory, modules over the Steenrod algebra and their Ext groups, finite H-spaces and compact Lie groups, and maps between classifying spaces and compact groups.