Quantitation capabilities of radioisotope X-ray fluorescence spectrometry (RXRFS) for determining lead, cadmium, tin, antimony, and barium in ceramic glazes were investigated. Twenty-one air-dried glazes and 85 fired glazes on test tiles were analyzed by using 109Cd and 57Co excitation sources. Accurate Pb determinations, with limits of detection (LODs) of about 0.3 mg/cm2 for 5 min counting times, were achieved by using the 75 keV K alpha 1 X-ray photopeak and a Pb foil calibration procedure. Cd, Sn, Sb, and Ba concentrations were determined with LODs from about 0.5 to 1.5 mg/cm2. For Pb and Ba, results obtained by using absorption corrections based only on element concentrations determined by RXRFS and an iterative approach led to analytical biases of < or = 4% relative to results obtained by using corrections based on known total element compositions. Biases were more severe for Cd, Sn, and Sb because lower X-ray energies were involved and sensitivities varied as a function of matrix Pb content. Pb concentrations were above LODs (1.3-40 mg/cm2) in 39 of 47 fired "food-safe" glazes and in 33 of the other 38 fired glazes (0.4-39 mg/cm2).