The results of an interlaboratory calibration of silica performed using commercial standards as samples are presented. The analytical values for silica concentration are consistent for lower concentration samples, but there are significant variations among the values for the higher concentration samples. The dilution technique is better than direct injection of high concentration samples to the atomic absorption spectrometer, although at present it is not possible to define the highest permissible silica concentration appropriate for direct measurements. High dilution factors also produce a high uncertainty in the analytical results. Therefore, the need still exists for conducting multi-laboratory calibrations over a wide range of silica concentrations to refine the precision and accuracy of silica analyses at high concentrations. (C) 2002 Published by Elsevier Science Ltd on behalf of CNR.