Objectives: The purpose of this study was to identify the complex periodontal treatment needs assessed by Periodontal Screening and Recording and the creation of a multivariate mathematic model that includes the risk indicators that explain such necessities in the patients inspected in the Admission Clinic at the School of Dentistry. Methods: A sample of 682 subjects (423 females and 259 males) was randomly selected. The subjects were interviewed regarding: age, gender, marital status, economic status, education and smoking habits in order to determine the relationship between these and complex periodontal treatment needs. One examiner previously calibrated carried out the clinical examinations in a dental chair with artificial light, pocket depth was measured with a periodontal probe Michigan “0” Williams graduation  at six locations around each tooth present. The complex periodontal treatment needs were estimated as the percentage of sites with a deep pocket  ³ 6 mm. Results: The subjects mean age was 45.92 ± 12.66, aged 30-88 years. The 22.8% of the subjects reported complex periodontal treatment needs with an extension of 62% (40.9 ± 12.6). The mean percentage of periodontal pockets were higher in males than in females (43.98 vs. 37.84, t=-2.43, p=0.0015) was observed, and these were significatively higher in smokers (48.87 vs. 37.84, t=-4.97, p=0.000). More over, a negative correlation was found between years of study and the extension of periodontal pockets (r=-0.089, p=0.000). In regards to age, a positive correlation was found (r=0.0428, p=0.000). No significant differences were found when the mean percentage of periodontal pockets was considered by marital status (p=0.089). Conclusions: The linear regression analysis for the construction of the model that explains complex periodontal treatment needs in this study population was conformed for three risk factors: age, education and smoking.