To permit facile N-15 solid-state NMR (ssNMR) analysis of the degree of acetylation (DA) of chitinous materials in fungi a method for the introduction of a N-15 isotopic label has been developed. Using Penicillium chrysogenum as a model system, a series of N-15-based media were surveyed for their abilities to support mycelial growth, and a rich medium supplemented with (H-15(4))(2)SO4 Supported good growth. Uptake of label into chitin extracted from mycelia grown in the rich (H-15(4))(2)SO4-based media was monitored by mass spectrometry, with similar to 1 g/l.. of (H-15(4))(2)SO4 leading to similar to 65% incorporation. The labeled chitin was studied by ssNMR to determine its DA, and the N-15 label permitted measurement of DA to within 0.5% with acquisition times of on the order of half an hour. Similar studies validated the method for DA measurements on chitin from cultures of Aspergillus niger and Mucor rouxii.