Abstract: In this paper, in contrast to the conventional practice of measuringporphyrins with side chain carboxylic groups in the form of their esters in CDCl₃ solutions,the proton and carbon-13 NMR spectra of hematoporphyrin.protoporphyrin and porphyrin c in acidic solvents are presented. This app-roach facilitates the structural identification and production monitoring ofthese medical porphyrins.