The invention provides cationic tetracyclic and pentacyclicbacteriochlorophyll derivatives (Bchls) containing at least one positivelychargedgroup and/or at least one basic group that is converted to a positivelycharged groupunder physiological conditions, preferably Bchls having an onium group derivedfrom a N-containing aliphatic or heterocyclic radical such as ammonium,guanidinium, imidazolium, pyridinium, and the like or a phosphonium, arsonium,oxonium, sulfonium, selenonium, telluronium, stibonium, or bismuthonium group,or a basic group that is converted to such onium groups under physiologicalconditions, said groups being bound to one or rnore of the positions 17 3, 132, 15 2and/or 3 1 of the Bchl molecule by ester or amide bond. The Bchls are usefulforphotodynamic therapy and diagnosis.
