In this preliminary study plasma osteocalcin levels and Tc-99m-HMDP (Technetium 99m hydroxymetylene diphosphonate) bone uptake (BU) were measured in 10 chronic end-stage renal failure patients who were on maintenance hemodialysis. The aim of this study was to determine the correlation between bone uptake and osteocalcin-a sensitive and specific marker of osteoblastic activity. There was a statistically significant increase in both 20 and 180 minute uptake in the patient group (36 +/- 2.7 and 39 +/- 3.6) when compared to the normal volunteers (32 +/- 3.1 and 19 +/- 2.7). Plasma osteocalcin levels were also significantly high (24.5 +/- 5.6 ng/ml) when compared with normal values (6.5 +/- 2.3 ng/ml). The correlations between osteocalcin and 20 and 180 min BU were high (r = 0.62 and 0.72 respectively). In conclusion, our preliminary study suggests that, in hemodialysis patients, Tc-99m-HMDP bone uptake quantification is a sensitive and non-invasive method for showing increased osteoblastic activity.