  The KEK to Kamioka long-baseline neutrino experiment (K2K) has begun its
investigation of neutrino oscillations suggested by atmospheric neutrino
observations. Twenty-eight neutrino events have been detected in coincidence
with the expected arrival time of the beam in the 22.5 kt fiducial volume of
Super--Kamiokande, the far detector at 250 km distance. The expectation is
37.8+3.5-3.8, derived using measurements of neutrino interactions in a near
detector and extrapolation using a beam simulation validated by a measurement
of pion kinematics after production and focusing. The background is of order
10^-3 events.
