  We present results from two long observations of XB 1746-371 by the Rossi
X-ray Timing Explorer (RXTE) in 2002 January and May, lasting 4 and 5 days
respectively. Dips are observed in the X-ray light curves with a depth of 25
per cent, largely independent of energy within the usable band of the PCA
instrument of 2.1 - 16.0 keV. X-ray bursting and flaring activity are also
evident. The dips define the orbital period of the system, and using a power
spectral analysis and a cycle counting technique we derive an accurate period
of P_orb = 5.16 +/- 0.01 hr. The previously-reported candidate period of
5.73$\pm$0.15 hr, obtained using Ginga data, is inconsistent with our
determination, perhaps due to the weakness of the dipping and the variability
of the source during that observation. The dips in the RXTE observations
presented here do not align with the Ginga period, however our improved period
is consistent with a wide range of archival data.
