I. Group Extensions, Simple Algebras and Cohomology.- II. Classifying Spaces and Group Cohomology.- III. Invariants and Cohomology of Groups.- IV. Spectral Sequences and Detection Theorems.- V. G-Complexes and Equivariant Cohomology.- VI. The Cohomology of the Symmetric Groups.- VII. Finite Groups of Lie Type.- VIII. Cohomology of Sporadic Simple Groups.- IX. The Plus Construction and Applications.- X. The Schur Subgroup of the Brauer Group.- References.