Procolipase is the precursor of colipase, which acts as protein cofactor for the activity of pancreatic lipase. The solution structure of procolipase has been determined by 1H NMR using two- and three-dimensional measurements. The secondary structure determination identified two separate three-stranded beta-sheet regions with concomitant hydrogen bond patterns. The tertiary structure of the protein was determined using 863 non-trivial proton--proton distance constraints, 14 hydrogen bond distance constraints and 55 phi and 25 X1 dihedral constraints. The structure that was obtained from distance geometry and energy refinement contains three highly disordered loops as well as a disordered N- and C-terminal region. The remaining part of the structure is well defined with a root-mean-square deviation (rmsd) relative to the average of 0.09 +/- 0.02 nm for backbone atoms (residues 11-30, 37-50, 57-69, 83-89). The protein comprises two identical domains, each containing a three-strand beta-sheet and two disulfide bonds: a 15-residue region in each domain superimposes with 0.07 nm rmsd, measured on backbone atoms. The solution structure is nearly identical to the crystal structure. It is in agreement with previous NMR data and, in combination with these data, supports the current model of procolipase micelle interaction and the lipase activation by colipase.