Radon (Rn-222) and thoron (Rn-220) were surveyed in indoor air of 15 public buildings and 10 homes in Slovenia in November 2004 by exposing Rn-Tn discriminative etched track detectors. The following ranges of the activity concentration were obtained for public buildings: 98-2680 Bq m(-3) for C-Rn, 19-1330 Bq m(-3) for C-Tn and 0.11-0.72 for the C-Tn/C-Rn ratio. In homes, the C-Rn range was 12-374 Bq m(-3) and all C-Tn values, except one of 29 Bq m(-3), were below the detection limit of 10 Bq m-3. Monthly effective doses in public buildings due to Rn (E-Rn) and Tn (E-Tn) were in the ranges 0.05-1.45 mSv and 0.01-0.47 mSv, respectively, and in homes, 0.018-0.548 and 0.009-0.095 mSv, respectively. The E-Tn/E-Rn ratio in public buildings was in the range 0.07-0.47
