Seventy-four Majolica sherds from fifteenth and sixteenth century sites in the Caribbean, Venezuela, Mexico, and Spain were analyzed for their lead isotopic compositions in thermal ionization mass spectrometer. Three groups are readily distinguishable based on the ratios of lead-208/lead-206 and lead-207/lead-206. Two groups consist almost entirely of samples from Spain and early colonial sites, including some specimens from the Mexico City Metropolitan Cathedral excavations. The third group includes specimens which, based on independent compositional analysis of the paste, were made in Mexico. Comparison of lead-isotope ratios of the glazes with published lead-isotope ratios for Mexican lead ores provides further confirmation of the suggested Mexican origin for specimens in this group.