A method is presented for estimating ingrowth on permanent horizontal sample points. The method yields an unbiased estimate of ingrowth under all forest sampling conditions, and differs from previous methods in that (1) only trees that are "in" and larger than the minimum dbh need be marked or tallied at any measurement, (2) no special accounting procedures are required for ongrowth or nongrowth trees, and (3) the difference between time-separated volume estimates is always equal to the sum of the growth component estimates. Thus, the "additivity" feature of permanent fixed-size plots is achieved. Forest Sci. 28:110-114.