Free base methyl pyridinium porphyrins were adsorbed on microscope glass slides, quartz plates or silicon wafers from a berate buffer solution at pH 10. Adsorption of the porphyrins is strongly enhanced by electrostatic interaction of the positively charged methyl pyridinium side groups with the SiO surface groups. Using UV-visible absorption spectroscopy, reflectometry and total internal reflection fluorescence (TIRF), the surface coverage, adsorption kinetics and the orientation of the porphyrins relative to the substrate surface were found to depend on the number and arrangement of the pyridinium groups attached to the porphyrin macrocycle, i.e. for the di-cis- (DiMPyP), the tri(TriMPyP) and the tetra- (TMPyP) methyl pyridinium substituted compounds. For all compounds the initial adsorption follows first-order kinetics. The limiting value of the absorbance of TriMPyP and TMPyP corresponds approximately to a full monolayer coverage. Adsorption of DiMPyP steadily increases beyond monolayer coverage at increasing exposure periods, however. TIRF measurements indicate that the TMPyP molecular plane is preferentially oriented parallel with respect to the surface on adsorption, in contrast to DiMPyP and TriMPyP which have a more random orientational distribution.