Abstract: Novel porphyrin derivatives of the general formula: ##STR1## wherein R.sub.1 each independently denotes a hydrogen, a C.sub.1 -C.sub.4 alkyl group or an ethenyl group, and R.sub.2 each independently denotes COZ(C.sub.m H.sub.2m)Q, COZCH(C.sub.m H.sub.2m Q).sub.2, --CH.sub.2 --Q [wherein Z is O, S or NH, m is an integer of 1 to 23, and Q is a di-(C.sub.1 -C.sub.4 alkyl)amino group or tri-(C.sub.1 -C.sub.4 alkyl)ammonium halide group] or ##STR2## (wherein X is a halogen); or R.sub.1 each independently denotes --C.sub.2 H.sub.4 --Q (wherein Q is the same as defined above), ##STR3## (wherein X is the same as defined above), and R.sub.2 each independently denotes a carboxyl group or a C.sub.1 -C.sub.4 alkoxycarbonyl group, and the production thereof are described. The quarternary ammonium salt type of the above compounds exhibit affinity and photosensitizing activity for cancer cells and can be employed for diagnosing and treating cancer under irradiation of laser light.