The segmentation cascade establishes the antero-posterior axis specification. The periodicity of the seven striped expression pattern of the segmentation pair rule genes is decisive to form the segments of the thorax and abdomen. However, in the presumptive anterior head region, no pair rule stripes are formed. Stripes are controlled by individual cis regulatory regions (CRMs), and we are working with the hypothesis that at least the CRMs of anterior pair-rule stripes are able to be activated but impeded to be expressed in more anterior regions of the blastoderm, due to the additive activity of several repressors such as sloppy-paired 1 (slp1) and huckebein (hkb). Our goal is to identify other repressors and investigate transcription regulation mechanisms underlying this network. Here we investigated the activity of tailless (tll). To accomplish that, we integrated different approaches: genetic and misexpression assays, bioinformatics and biochemistry. We used an image computational tool to detect small perturbations of pair-rule striped patterns and gap domains in different genetic backgrounds. With that we were able to detect small deviations for anterior most pair-rule stripes of hairy (h) and even-skipped (eve). h 1 and eve 1 are anteriorly derepressed in tll- and increased effects were detected in slp-;tll- embryos, consistent with repression roles of Tll. We further confirmed that using reporter constructs under the control of h 1 and eve 1 CRMs in the genetic assays. Indeed, with a tll misexpression system we confirmed tll repression on these CRMs. We also investigated anterior gap genes in different genetic backgrounds and with the misexpression system. We did detect Tll effects on empty-spiracles (ems) and buttonhead (btd) in these assays, but not consistent with Tll indirect roles on h 1 and eve 1. These results point to Tll as being part of an anterior repression mechanism restricting anterior pair-rule stripes CRMs in the anterior blastoderm. Moreover, during our investigations with the misexpression system, we also detected repression effects for the majority of the other pair-rule stripes as well as for central gap genes, although we did not detected derepression for these putative targets in tll- or even in slp-;tll- double mutants. We discuss the physiological relevance of Tll also being a repressor to impede the expression of central pair-rule stripes and gap domains at the ends of the embryo. Financial support: FAPESP.