The El Niño-Southern Oscillation (ENSO) phenomenon is believed to be a significant cause of year to year climate variation, which greatly impacts agricultural productivity. The unusually strong El Niño event in 1997-98 and the strong La Niña event that followed in 1998-99 both led to economic consequences for US agriculture. This paper applies a stochastic economic model to estimate the extent of economic damage, deriving predicted losses to be $1.5 to $1.7 billion for El Niño and $2.2 to $6.5 billion for La Niña.