Particle counts were performed on 1,000 intravenous administration sets from ten suppliers on the Swiss market using a HIAC/Royco electronic counter. The following main conclusions may be drawn from the results of this study: --the small particles were the most numerous, regardless of the type of set; --the differences in the counts obtained for the different suppliers' sets tended to level off for particles larger than 10 microns; --the drip chamber and latex connector may be two important sources of particles; --the particulate contamination from the sets is relatively low compared with the amount of particles contained in the parenteral solutions.