To answer the question how often runt eggs are produced by Northern Goshawks, a large sample of egg measurements was collected from several regions in The Netherlands (Table 1: 1011 eggs from 326 nests). According to the criterium that eggs less than 75% of the average egg size in the sample are runt eggs, seven such eggs were identified. However, a frequency distribution of egg volumes (Fig. 1; 16.2-71.4 cc) showed that four presumed runt eggs actually fell within the normal range of egg volumes (measuring 67-71% of the average volume); one of these four hatched, the remaining three did not. Three eggs fell well outside the normal range of egg volumes (29, 53 and 53% of the average volume), and are considered to have been runt eggs (none hatched). One of these was the first-laid egg in a clutch of two, in which the second egg was rather large (60.6x44.5 mm, 66.1 cc) but did not hatch either. The runt egg in this clutch contained a particle of yolk, the second egg contained a full yolk but showed no embryonic development. No such information is available for the remaining runt eggs.