The Motion Control 3500 line in our laboratory was fitted successively with a pinch sampler then a universal sampler. The precision of the results obtained with this HVI line fitted with the different samplers was evaluated. Roller-ginned samples required considerably more measurements to obtain the same precision as those that had been saw ginned. A comparison of the within-sample variances showed that the results obtained with the universal sampler were less precise than with the pinch sampler for saw-ginned cottons. The precision of the two systems was identical for roller-ginned samples.