Voltammetric and amperometric techniques have been used for the systematic optimization of chemically modified screen-printed carbon electrodes (SPCEs) with regard to the determination of H2O2. A variety of metallophthalocyanines were incorporated into the base carbon matrix with a view to selecting the most efficient redox catalyst for H,O, oxidation. Sensor tailoring with organometallics accelerated the rate of this process; typical reductions in overvoltage were in the 700, 800 and 900 mV (vs. saturated calomel electrode (SCE)) regions for cobalt-, manganese- and iron-containing phthalocyanines respectively, when compared with their unmodified counterparts. The considerable faradaic activity of the redox mediators was further demonstrated by the rapid, sensitive and reliable steady state responses to concentrations of H2O2 over an analytically useful range. A mechanism for the catalytic processes has been postulated on the basis of voltammetric, amperometric and X-ray photoelectron spectroscopic evidence. The precision of sensor fabrication and stability were also investigated.