In this study, the effects of trans fatty acids (TFAs) on rheological properties of dough (elastic moduli (G'), loss moduli (G''), complex modulus (G*)) and textural properties of dough and cookie (hardness) were studied. Two different groups of fat samples having different TFA composition but similar solid fat content (SFC) were prepared. Samples of the first group (group 1) had TFA between 0.0 and 56.23 %, while the samples of the second group (group 2) contained trans isomers ranging from 0.0 to 44.40 %. Texture measurements of different doughs and cookies prepared with different fat samples were performed. Texture measurements indicated that hardness values of doughs increased from 3950 +/- 420 to 5498 +/- 506 g in group 1 and 4700 +/- 501 to 6787 +/- 369 g in group 2 with increased amounts of TFAs. A particularly high, almost three-fold increase in complex modulus values was observed in the dough samples containing the highest TFA levels compared with samples containing 0.0 % TFA. Although not significantly different, mean hardness and relative sound intensity values of cookies displayed an initial decreasing trend and then both parameters had maximum values when the TFA content was at maximum in both groups.