AbstractA comparison of the regular spectral transmittance scales of National Institute of Standards and Technology (USA), Institute National de Metrologie (France), National Research Council (Canada), and All‐Union Research Institute for Optical and Physical Measurements (CIS) was accomplished using neutral glass filters with transmittances ranging from approximately 0.92 to 0.001. Storing the filters for almost four years produced no conclusive evidence of improvement over a previous interchange between NIST and three different national standardizing laboratories when the filters were stored for only 30 days. The agreement ranges from 0.01% to 0.3% depending on the laboratory and the filter used. The uncertainties (99.7% estimated confidence level) are generally greater than the differences between NIST and the individual laboratories. The sample‐induced error contributed 20% or more of the total uncertainty except for a few cases as found in the previous comparison. This interchange, similar to the previous one, is part of an ongoing effort to obtain international standardizat