  The kilohertz quasi periodic oscillations (QPOs) discovered in several low
mass X-ray binaries (LMXBs) by the Rossi X-ray Timing Explorer (XTE) are
thought to occur at the orbital frequency in accretion discs whose inner edge
corresponds to the innermost (marginally) stable orbit allowed by general
relativity. These ideas have been applied to constrain the equation of state
(e.o.s.) of the central neutron star. Here we discuss another possibility, that
the central object is a strange star, and show how kHz QPOs constrain the
e.o.s. of strange matter.
