Measurements of 210Po embedded in glass have been performed with passive detectors in houses ofthree rural communities of Yugoslavia. Field work has been initiated and carried out by the VincaInstitute, Belgrade and analyses have been conducted by SSI (Sweden), UCD (Ireland), NRPA(Norway) and CRR (Italy). Based on 210Po concentration assessments, radon retrospective estimateshave been produced. Fairly good agreement amongst laboratories resulted both for polonium andradon determinations.