Some major problems in the calculation of structures and properties of peptide molecules have been reviewed. Recent results from empirical calculations and extended basis set ab initio calculations have been summarized. The importance of fully flexible geometry and vibrational free energy has been discussed as has the effect of explicit Inclusion of the solvent molecules upon the conformation of peptides. Finally, the problem of "folding" a protein, i.e. predicting Its tertiary structure from Its primary sequence, has also been reviewed along with the description of a new technique which avoids the structural oversimplifications employed by other workers, at least as far as the backbone Is concerned. Although this procedure requires further Improvement, preliminary results are reported for pancreatic trypsin Inhibitor, myoglobin and serine proteases