Aim: In this study, we aimed to reveal the sequence analysis of 69 pharmacogenes in 635 patients and the clinical explanation of variants. Materials and methods: Genomic DNA was isolated from peripheral blood of patients. Next-Generation Sequence analysis and bioinformatic analysis were performed to identify 69 pharmacogene variants. Variants with clinical annotation were identified. Results: Analysis of 69 pharmacogenes in a total of 635 patients identified 9485 variants. The number of distinct variants identified in each gene was 1409. Of these 1409 variants, the number of variants registered in PharmGKB was 126. Among the 126 variants registered in PharmGKB, 26 variants were identified that had a direct association with clinical annotation and drug efficacy or toxicity. The most common variant genes were DPYD, CYP2C19, VKORC1,UGT1A1, RYR1 and MTHFR. These 26 variants with clinical annotation were identified in 327 (51%) different individuals. Conclusions: Such a high frequency of critical variants (51%) points to the need for pharmacogenetic studies. The results are extremely important in terms of determining the drug dose according to the genomic status of individuals receiving drug therapy and preventing unnecessary health expenditures.