Haversian canal plugging is a common lesion in bone from human radium cases, signaling vascular damage. Its incidence is correlated with the whole body radium dose. However, since the vascular supply to bone forms an extensive anastomotic plexus facilitating propagation of vascular damage from a primary site of high radium content, we do not know if the degree of plugging is related to the local bone dose. In this report, we compare the incidence of plugging of osteons in different regions (16 sections) of humeri of three radium cases with terminal 226Ra body contents of 0.203, 1.03 and 15.4 muCi to the local dose of radium in adjacent bone sections. While the first and third subjects had received 226Ra only, the second had had a large intake of 228Ra as well. The background incidence of plugging in 35 "normal" humeri from dissecting room populations (45-90 yr) ranged from 0 to 1%, with an average of 0.3%. The least squares linear regression equation for the relation between the percent of canals plugged (PCP) and dose, PCP = (0.00214 +/- 0.00014) rad + (3.26 +/- 3.6), predicts for our three radium cases a development of about 0.002% plugs/rad. The correlation coefficient was very high (r = 0.97, n = 16, P less than 0.01). When normalized to radiation dose from the two decay series, 226Ra and 228Ra appear to be equally effective in producing plugged canals.