The purpose of this study was to assess the degree of pain during periodontal probing and mechanical non-surgical therapy according to age, gender, and intersubject variation such as tooth type, tooth surfaces or regions of mouth, probing depth, and bleeding on probing. The study was carried out on 64 patients with chronic periodontitis. Pain/discomfort of patients during both periodontal probing and scaling and root planing (SRP) was measured using a visual analog scale (VAS). During periodontal probing and SRP, VAS scores decreased with increasing age for two procedures (Spearman rho, -0.301 and -0.348, respectively; P < 0.01). VAS scores were considerably lower for oral sites than for facial sites. VAS scores in probing were significantly higher in sites > or =4 mm deep than sites <4 mm deep. Sites bleeding on probing had a significantly higher VAS scores than sites no bleeding on probing (p < 0.05). The results showed that although there is no difference between genders, the intensity of pain during periodontal probing and SRP was different dramatically between patients as well as vary between different locations in the same mouth. If pain responses for probing in different several regions in the same mouth during initial examination were noted into patient chart used for initial examination, the therapist will recognize patients with elevated pain responses. If need be, they will then apply some pain control medication or anesthetic for patients during probing and SRP.