Aim. The aim of this study is to compare the severity of tissue reaction in anterior abdominal wall caused by synthetic meshes in different fiber thickness. Methods. In all rats, abdominal wall along the midline, skin and subcutaneous tissue was incised 2 cm along and a 3x3 cm2 area was dissected. Group I: Only dissection was applied. Group II: A 2x2 cm2 diameter mesh with 320 micron mesh thickness was placed on the dissected area. Group III: A 2x2 cm2 diameter mesh with 600 micron mesh thickness was placed on the dissected area. Results. Infection and seroma frequency in incision line was defined as, In Group I (15 %) in three rats, in Group II (25 %) in 5 rats and in Group III (35 %) in 7 rats. Measured plasma IgE levels in rats were found meaningfully high compared to that of control group (p<0.05). The value of thin mesh group was found meaningfully low compared to that of thick mesh group (p<0.05). A meaningful difference was not observed among the leucocytes values of the groups (p<0.05). The fibrosis measurements in group III was higher than that of the other group (p<0.05). Conclusion. Reaction has occurred for both meshes. It has been observed that the reaction occurred in thin mesh group was meaningfully lower compared to the thick mesh group as a result of serological tests, electron and light microscopic examinations. Referencing this, it has been understood that the reaction occurred has shown parallelism with the mass of mesh.