Previous studies on the role of lactose malabsorption in the pathogenesis of postmenopausal osteoporosis have yielded conflicting results and further information is needed. To date, all studies have been carried out on populations with a low prevalence of lactose malabsorption and the lactose intestinal absorptive capacity was tested using a non-physiological dose of lactose. In fifty-eight Italian postmenopausal women (mean age 57 (SD 7) years), bone mineral density (BMD) at lumbar spine, H2 breath response after ingestion of 20 g lactose, intensity of symptoms of intolerance after a lactose load and daily Ca intake were evaluated. No differences were found between women with or without a positive H2 breath test with regard to BMD (-1.2 (SD 0.9) v. -0.9 (SD 0.8)) and Ca intake (509 (SD 266) v. 511 (SD 313) mg/d). On the contrary, both BMD and Ca intake were significantly lower in women with lactose malabsorption and symptoms of intolerance (-1.5 (SD 0.7) and 378 (SD 220) mg/d) than in those with malabsorption without symptoms (-0.9 (SD 0.9) and 624 (SD 254) mg/d). Moreover, in lactose malabsorbers Ca intake was correlated inversely with symptom score (rs -0.31, P < 0.05) and positively with BMD (rs 0.42, P < 0.005). Our results show that in Italian postmenopausal women Ca intake and BMD are not influenced directly by lactose malabsorption; the appearance of symptoms of intolerance seems to influence BMD unfavourably through a reduced Ca intake.