The photocatalytic oxidation of phenols by oxygen has been studied in alkaline aqueous medium upon irradiation with visible light. Metal Zn(II) and Al(III) mono- and polynuclear phthalocyanine complexes, soluble in water, have been used as photocatalysts. The studied polynuclear complexes represent two-dimensional polymers, formed of condensed phthalocyanine macrocycles. The number of the phthalocyanine units in them is 3 or 4. No visible batochromic shifting is observed in the Q-band electron transition (lambda= 665-680 mn) of the polynuclear complexes with respect to their mononuclear analogues. This fact is an indication of a low pi-pi electron delocalization between the phthalocyanine units of the polynuclear complexes in the excited state. The photocatalytic activity per mole of the polynuclear complexes at pH = 7 or 13 is much higher than that of the respective mononuclear phthalocyanine complexes. The high photocatalytic activity of the polymers might be explained by the proceeding of an intra-molecular triplet-triplet energy transfer between the phthalocyanine macrocycles in accordance with the mechanism of Dexter. The singlet oxygen, obtained by photon-induced energy transfer from the excited mono- and polynuclear photosensitizers, dominates the initial steps of photooxidation.