A microanastomosis might tolerate a torsion up to 360 degrees, but the effects of arterial microanastomosis torsion on the survival of the flap it supplies are unclear. The aim of this study was to investigate the consequences of microarterial anastomosis torsion on the groin flap in rats. Forty Sprague-Dawley rats were divided into five groups. An oblique groin flap was harvested as an island flap and a patch-to-side arterial anastomosis was performed with torsion angles of 0 degrees, 90 degrees, 180 degrees, 270 degrees, and 360 degrees. Six of eight flaps in Group I (0 degrees torsion), six of eight flaps in Group II (90 degrees), three of eight flaps in Group III (180 degrees), and none of the flaps in Groups IV and V (270 degrees and 360 degrees) were found to be viable after 1 week. The patency and flap survival rates observed in Groups II, III, IV, and V were compared with those in Group I using Fisher's exact test. The patency rates and flap survival rates in Groups IV and V were significantly lower compared with those in Group I. Our data show that skin flaps can survive even if their arterial pedicle is anastomosed with a torsion of up to 180 degrees.