The recent article by Cadle et al. (1975) describes a comparison of different types of condensation nucleus counters. Some general remarks are made here on the terminology and calibration of the counters and on the interpretation of the results. A comparison of one of the calibrated instruments (SANDS) with the UMR Absolute Aitken Nuclei Counter (UMR-AANC) in Rolla just after the described workshop showed steadily lower counts by SANDS (about 30% lower). This enables one to compare indirectly the UMR-AANC with the other counters.