Introduction: The gingival biotype of a population is important epidemiological data for the best treatment planning, while preserving periodontal health. In Peru there is a shortage of similar data published. Objective: To determine the prevalence of gingival biotype in adult patients of the Dental Service of the Victor Lazarte Echegaray and Hospital Regional Docente de Trujillo, April - June 2018. Materials and Methods: This cross-sectional, descriptive and observational study included 200 patients from the Dentistry Service of the Victor Lazarte Echegaray and Hospital Regional Docente de Trujillo. Using the accidental non-probabilistic selection method, the gingival biotype was evaluated through the transparency of periodontal probe technique. To determine the reliability of the method the Kappa statistic was used, finding an inter-evaluator reliability of 0.750 and intra-evaluator of 0.762. Descriptive statistics were used for the results, presenting absolute and percentage frequencies. Results: The prevalence of the thick gingival biotype was 57.5%. Males and females presented predominantly a thick biotype, 63.1% and 54.8% respectively. The groups of 18 to 29 and 30 to 39 years old presented 62.1% and 64.5% a thick biotype, respectively. On the other hand, the majority of people 40 to 50 years old presented a thin gingival biotype (52.8%). Conclusions: The thick gingival biotype was predominant in both sexes and in both hospitals. Also, gingival biotype varies with age, with the thick biotype more prevalent in younger age groups.