Anatomico-pathological and radiological studies of osteopoikilosis were performed in two cases, one involving a femoral head, excised after a fracture of a femoral neck, in an elderly man and the other following biopsy of an iliac crest in a young woman. In both patients wide-spread radiological evidence of the disorder was present as an incidental finding. The radiological appearance of rounded and linear densities corresponded to old and inactive remodelling of spongy trabeculae in epiphyseal and metaphyseal locations. The distribution and appearance of these osteopoikilotic densities suggested them to have been related intimately to mechanical strain on spongy bone trabeculae. The diffuse nature of the lesions, their hereditary character, and their possible association with abnormalities of the skin suggest the existence of a particular terrain in which general metabolic conditions of connective tissue may interact with mechanical stresses in bone. Careful analysis of the findings in osteopoikilosis is desirable in order to provide data concerning the physiopathology of the skeleton and to permit more definitive interpretation of localised areas of bone condensation, including those observed not only in solitary bone islands and such conditions as osteopathia striata, but also those associated with infections and tumours.

Aims:To evaluate the proliferative activity of urothelial neoplasms, compare it with that of the normal urinary tract epithelium, and determine its relation to morphological grade and presence of invasion. Methods: Multiple biopsy specimens from 53 individuals-eight normal controls, five patients with severe urothelial atypia, and 40 with transitional cell carcinomas (TCCs)-were studied using in vitro bromodeoxyuridine (BrdU) incorporation, Ki67 antigen expression, and quantitation of the nucleolar organiser regions (NORs). Results: The percentage of nuclei labelled by BrdU (BrdU index) correlated well with the percentage of nuclei expressing the Ki67 antigen (Ki67 index). These proliferation indices were very low (less than 0-1% in 60% of samples) in the urothelium of normal controls and the morphologically unremarkable epithelium of patients with TCCs. Non-invasive TCCs had increased proliferation (BrdU index 6-32 (SD 0-8)%, Ki67 index 5 04 (0.6)% but lagged behind the invasive tumours (BrdU 20-9 (3-2)%, Ki67 18*6 (2-8)%). The average NOR count was 1-57 (0-03) in mor-