  We report on the determination of the visual orbit of the double-lined
spectroscopic binary system 64 Piscum with data obtained by the Palomar Testbed
Interferometer in 1997 and 1998. 64 Psc is a nearly equal-mass double-lined
binary system whose spectroscopic orbit is well known. We have estimated the
visual orbit of 64 Psc from our interferometric visibility data. Our 64 Psc
orbit is in good agreement with the spectroscopic results, and the physical
parameters implied by a combined fit to our interferometric visibility data and
radial velocity data of Duquennoy and Mayor result in precise component masses
that agree well with their spectral type identifications. In particular, the
orbital parallax of the system is determined to be 43.29 \pm 0.46 mas, and
masses of the two components are determined to be 1.223 \pm 0.021 M_{\sun} and
1.170 \pm 0.018 M_{\sun}, respectively.
  Nadal et al. put forward arguments of temporal variability in some of the
orbital elements of 64 Psc, presumably explained by an undetected component in
the system. While our visibility data does not favor the Nadal temporal
variability inference, neither is it definitive in excluding it. Consequently
we have performed both high dynamic-range near-infrared imaging and
spectroscopy of potential additional companions to the 64 Psc system. Our
imaging and spectroscopic data do not support the conjecture of an additional
component to 64 Psc, but we did identify a faint object with unusual red colors
and spectra.
