Measurement of B(K -> pnn)
  The experimental measurement of positive kaons decaying to a positive pion and a neutrino, anti-neutrino pair (pnn) is reviewed. Recent results from experiment E787 at BNL are presented: with data from 1995--97 the branching ratio has been measured to be B(pnn) = (1.5^{+3.4}_{-1.2}) \times10^{-10}. The future prospects for additional data in this mode are examined. 
S. Kettell (BNL)