The AA. have studied biological effects of Laser radiation and Haematoporphyrin (HPD) on Salmonella typhimurium TA 100 strain. Their results do not show a growth of letal effect that they demonstrated on antecedent trials, only dependent from Laser radiation. Nome mutagenetic effect was demonstrated. They think that HPD is not capable of binding or penetrating in bacterial cell owing to complexity of bacterial capsule and wall; therefore HPD can not increase Laser radiation effect, though its photodynamic action.