A measurement is presented of the two-jet differential cross section d3σ/dETdη1dη2 at center of mass energy s√=1800 GeV in pp¯ collisions. The results are based on an integrated luminosity of 86 pb-1 collected during 1994 to 1995 by the CDF Collaboration at the Fermilab Tevatron collider. The differential cross section is measured as a function of the transverse energy ET of a jet in the pseudorapidity region 0.1<|η1|<0.7 for four different pseudorapidity bins of a second jet restricted to 0.1<|η2|<3.0. The results are compared with next-to-leading order QCD calculations determined using the CTEQ4 and MRST sets of parton distribution functions. None of the sets examined in this analysis provides a good description of the data.