By means of panoramic radiography (PR), the frequency and location of interproximal infrabony defects (IPIDs), their relationship with age, gender and remaining teeth were Studied in 416 individuals seeking dental care. The presence/absence of IPIDs and the defect depths were evaluated Oil mesial and distal surfaces of a total of 8,964 teeth. One or more infirabony defects were recorded oil 23% of the PRs (96 individuals, 152 IPIDs). The frequency of infirabony defects <= 3 mm, 3-5 mm and >= 5 mm was 12.5%, 9.6% and 3.6% respectively. The number of infrabony defects >= 5 mm was significantly lower than infirabony defects in <= 3 mill and 3-5 mm groups (p<0.05). The difference between the frequency of IPIDs among two genders was non-significant (20.6% for females, 26.8% for males). The IPIDs were most prevalent in the oldest group (>50 years), which also presented with significantly more missing teeth (p<0.05). The most frequent locations for IPIDs were maxillary and mandibulary molar teeth.