Objective: The goal of this study was to determine the genetic variability of the fimA gene in Porphyromonas gingivalis isolates from Spanish patients. Study Design: Pooled subgingival samples were taken, processed and cultured in non-selective blood agar medium. Pure cultures of one to six isolates per patient were obtained and PCR and PCR-RFLP were used for fimbrillin gene (fimA) type determination of the extracted genomic (DNA). Results: Two hundred and twenty four Porphyromonas gingivalis isolates from 65 patients were analyzed consisting of 15 non-periodontitis patients (66 isolates) and 50 with periodontitis (158 isolates). Genotype II was the most prevalent (50.9%), while the other types of fimbriae did not exceed fifteen percent of prevalence. Isolates with types II and IV of fimbriae were significantly more prevalent in periodontitis patients than isolates with genotype I. Co-infection was observed in 17.65% of the patients analyzed. Conclusion: The results suggest that in this population Porphyromonas gingivalis with type II of fimbriae are significantly more predominant in periodontitis patients than genotype I.