Search for orbital X-ray variation in SCO X-1

All 5 yrs of 3 to 6 keV monitoring of Sco X-1 by the Ariel 5 all-sky monitor were reanalyzed, to search more sensitively for variation at the 0.787313 day orbital period. The best limits on orbital variations come from data selected to exclude active episodes. Any narrow absorption dip has an average depth 1.0% 0.1/Delta Phi - (2 sigma) where Delta Phi is the dip width in units of the orbital period. A weak (0.4%) sinusoidal modulation, with 3.2 sigma significance, reaching minimum at phase 0.59 + or - 0.06 with respect to superior conjunction of the optical emission line source is observed. The upper limit to a sinusoidal orbital modulation is 0.7%. Sco X-1 never (at least not for more than 2 hr) dips below its normal quiescent level.