Small intestinal submucosa (SIS) is a promissory material that has been used experimentally for guided tissue regeneration. The purpose of this study is to evaluate and compare the behavior of SIS in a tensile test. Methods: The SIS material was prepared following the methodology suggested by Badylak and dehydrated in laminar flow for 12 h. The SIS membranes were disinfected with a solution of 0.5% H2O2 with NaOCl and sterilized with EtO. The resultant biomaterial was acellular. 13 specimens (11×33 mm) were prepared and randomly divided into 3 groups. The first one (n=4) was dry, the second one (n=4) was incubated at 37°C and 5% CO2 with Dulbecco's modified Eagle's media for 4 weeks. The last one (n=5) was seeded with fibroblasts from HT1080 cell line from a fibro-sarcoma and incubated for 4 weeks. Tensile tests (50 mm/min) were performed. Results: The resultant stress-strain curves showed elastic and plastic deformation simultaneously. The first part of the curves was characterized with an exponential regression. In the first group the exponent was 27.47±6.13 (mean ± SD), in the second group was 9.39±1.52 and in the third group was 11.30±4.30. The statistical analysis included a one-way ANOVA with SIS treatment (dry, wet, seeded) as the independent variable and the dependent variable was the exponent of the curve. A Duncan's multiple range test showed significant differences between all pairs of means except the pair seeded-wet. In the dry group the slope was significantly greater, therefore the elongation before break increases in the wet and seed specimen.