In addition to the uncertainty propagation method provided by the GUM (Guide to the expression of uncertainty in measurement) witch requires the modelling of the measurement process, the inter-laboratory experimental method is a good solution to deal with the uncertainty of a measurement technique, in given conditions. This method is commonly frequently used in some fields (eg. in chemistry); it is managed with ISO standards and technical notes or specifications. Thus, inter-laboratory comparisons in hydrometry allow the quantification of uncertainty due to errors that will be expressed in repeated simultaneous gauging operations. These repetitions have to be done by different teams, at the same time, in stable flow conditions, under repeatability and reproducibility conditions. Simple formulae with repeatability variance and the inter-laboratory variance results assessed to evaluate the gauging technique uncertainty, supposed to be unbiased. The bias or systematic error is linked to the gauging technique; it could be evaluated by comparison with an independent flow measurement technique with a known uncertainty. In this study some suggestions are presented for the hydrometric inter-laboratory comparison organisation. These pieces of advice follow from recent inter-laboratory comparison with ADCP, current meter on wading rod or gauging van, and tracer dilution devices. The inter-laboratory comparison method is a standardised solution for improving the knowledge and the uncertainty evaluation of gauging techniques.