The method consists in visual examination of the external surface of beans to identify those which have been damaged by insects. Determination of the observed proportion, as a percentage, of damaged beans and, if possible, identification of the species of insect responible to damage. From the proportion of damaged beans thus determined: estimation of the confidence limits of the true proportion of damaged beans for a given probability; estimation of the probability that the true proportion of damaged beans will not exceed a given value. An annex A shows illustrations of damaged beans. An annex B describes a test for homogenity of the laboratory sample.