: Perianal Crohn's disease is frequently associated with complex fistulous tracts and deep abscesses which are often difficult to identify by clinical-proctological examination or anal endosonography. In a prospective study we examined the value of MRI in perianal Crohn's disease as compared to proctological and intraoperative findings. MRI of the perianal region was performed on 54 patients with active perianal Crohn's disease. Fistulas and abscesses were classified according to the anatomical region. The results were then compared with clinical and/or intraoperative findings. A total of 90 fistulas and 83 abscesses were found. MRI detected all abscesses and 82% of the fistulas. 30% of the abscesses and 26% of the fistulas were missed by clinical examination. MRI was less sensitive in detecting short transsphincteric fistulas, especially anovaginal fistulas. MRI is a painless procedure without radiation exposure. These features are important additional advantages in comparison to endosonography or CT. We believe MRI is the imaging method of choice in patients with active perianal Crohn's disease where the proctological examination including anal endosonography is inconclusive.