Aim: A pilot clinical trial was performed to determine (i) microbiological and clinical efficacy (ii) confort of One Stage scaling and root planing vs. multiple SRP sessions, in smoker patients with chronic periodontitis. Material and Methods: Nine smoker patients, men and women, between 40 to 70 years old, systemically health, with mean deep pocket ≥4mm, attachment loss, bleeding on probing, diagnosed with chronic periodontitis moderate to severe based on American Academy of Periodontology (A.A.P.), were randomized into two groups for scaling and root planing, group A for full-mouth, and group B per one week. Deep pocket, clinical attachment lost, bleeding on probing was measured. Subgingival samples were taken from deepest pockets before and six months after treatment. Patients were asked with a survey about comfort of the treatment in both groups. Results: Group A showed mean deep pocket decreased in 0.88mm, clinical attachment lost in 1.12mm, bleeding 7.52% initial average respect. Group B, did not show changes respect initial measures, in contrast with bleeding, it has decreased in 0.5%. Both groups had showed similar decrease in prevalence of: Aggregatibacter actinomycetemcomitans (33%), Porphyromonas gingivalis (22%) Prevotella intermedia (22%), Fusobacterium species (55%), Eikenella corrodens (44%), Gram negative enteric rods (11%). Group B has referred better comfort than group A, during the treatment. Conclusion: Although there was no statistically significant differences, there was a trend showing that the Full-mouth scaling and root planning got better clinical and microbiological efficacy than scaling and root planing in multiple sessions, but had shown lower comfort around the treatment.