The invention provides anionic water-soluble tetracyclic and pentacyclic bacteriochlorophyll derivatives (Bchls) containing at least one, preferably two or three, negatively charged groups and/or acidic groups that are converted to negatively charged groups at the physiological pH, preferably Bchls having a group COO - , COS - , S0 3 - , PO 3 2- , COOH, COSH, SO 3 H, and/or PO 3 H 2 bound through an ester or amide bond to one or more of the positions 17 3 ,13 3 , and 3 2 of the tetracyclic or pentacyclic Bchl molecule, for photodynamic therapy and diagnosis.
