  A search for events containing an isolated electron or muon and missing
transverse momentum produced in ep collisions is performed with the H1 and ZEUS
detectors at HERA. The data were taken in the period 1994-2007 and correspond
to an integrated luminosity of 0.98 fb^-1. The observed event yields are in
good overall agreement with the Standard Model prediction, which is dominated
by single W production. In the e+p data, at large hadronic transverse momentum
PtX >25 GeV, a total of 23 events are observed compared to a prediction of 14.0
\pm 1.9. The total single W boson production cross section is measured as 1.06
\pm 0.16 (stat.) \pm 0.07 (sys) pb, in agreement with an SM expectation of 1.26
\pm 0.19 pb.
