The usual time interval between the administration of Tc-labeled bone-seeking radiopharmaceuticals and imaging varies among nuclear-medical departments. Pharmacokinetic data indicate that the interval could be as short as 2 h. The overall quality of bone detail was studied in 280 bone scans performed at intervals from 2-5 h following injection of 99mTc diphosphonate. No significant qualitative difference was found between studies at 2 h and those at later intervals.