A procedure is described to avoid artifacts due to instabilities when measuring submicron particles (SMP) by mean of resistance pulse instruments (CoulterÒ principle). The sample has to flow for at least half an hour before recording the counts given by the equipment. The concentrations of SMP obtained with this procedure are similar to those obtained with image analysis by SIERACKI & VILES(1 992) but more than one order of magnitude lower than those given by KOIKE et al. (1990). The discrepancies with the results of KOIKE et al. (op. cit.) are concentrated in the smallest SMP. Therefore, our results leads us to suggest caution when considering the role of SMP in the biogeochemical cycling of elements in the ocean.