We simultaneously measure the gravitationally-induced phase shift in two Raman-type matter-wave interferometers operated with laser-cooled ensembles of $^{87}$Rb and $^{39}$K atoms. Our measurement yields an Eotvos ratio of $eta_{text{Rb,K}}=(0.3pm 5
.4)times 10^{-7}$. We briefly estimate possible bias effects and present strategies for future improvements.
