This paper deals with Bitterlich's angle-count method of estimating the basal area proportion in forestry. In § 1 the sampling distribution of the estimator is derived on the assumption that the trees are distributed randomly, and in §2 the angle-count estimator is compared with the more conventional one based on sample plots. In the next section the results are illustrated in a more concrete form by choosing a specific distribution for the radii of the trees. The effect of the major practical drawback of the method is studied in §4 and in the final section the behaviour of the angle-count estimator is considered, in the case where the spastial distribution of trees is regular rather than random.