In order to elucidate dental care behavior related to interdental cleaning, a group of first-year students were invited to a free dental examination. 186 of the students invited (76%) were examined clinically and roentgenologically. The mean DMFS-index of the students was 22.6 (+/- 12.6). They were also asked about their use of dental floss. 35% of the students reported using dental floss, but only 2% reported daily usage. 45% of the students had been taught how to use dental floss, and 83% of these had been taught by dental personnel. Teaching had no effect on the reported frequency of use. There were no statistically significant differences in the occurrence of dental plaque and gingivitis between those who used dental floss and those who did not. The subjects were unable to use dental floss on 1 out of every 3 filled proximal surfaces of the first molars. No correlation could be found between dental caries experience and the reported use of dental floss.