A course for the last year undergraduate and M. Sc. students. This course focuses on how an amino acid sequence of a protein determines its 3-Dimensional structure. The course introduces principles of protein structure, protein folding in the cell, and thermodynamic and kinetic methods for studying protein folding in vitro. Additional topics covered are roles of helper proteins such as chaperonins and isomerases, and diseases associated with protein folding defects. The most recent advances in the field are discussed.