The results of an interlaboratory comparison of measurements of relative spectral sensitivity of vacuum photocells are summarized. The comparison was part of the work of the CIE Photometry and Radiometry Committee (TC-1.2). Nine laboratories measured two cells each. The results were corrected for the drifting of relative spectral sensitivity of each cell. The standard deviation of an individual measurement on a cell without filter was less than 2% from 450 nm to 620 nm, increasing to 5% at 390 nm and 690 nm. The standard deviation was larger for a V(lambda) corrected cell, being less than 2% in the range 490-600 nm and increasing to 5% at 475 nm and 660 nm. The largest errors were probably caused by wavelength and bandwidth errors.