Soil and plant based measurements of crop water status were used to evaluate varietal responses to four contrasting soil moisture regimes in 1996 and 1997. Premature irrigation cut off resulted in significantly more extraction of residual soil moisture and higher accumulated crop stress mid- and late-season. Extending the irrigation termination date beyond optimum timing, determined by a computer simulation module, resulted in greater numbers of unharvested bolls, which corresponded closely with numeric decreases in cotton yield for these treatments. An accumulated stress bar day concept is proposed that uses average weekly pressure chamber readings summed daily from post bloom through defoliation. Accumulated stress bar days in 1996 and 1997 showed a correlation with yield of R² = 0.950 and 0.945, respectively. Percent allowable depletion did not correlate well with crop water stress and measured by the pressure chamber. This paper demonstrates the value of using measurements of leaf water potential to schedule irrigation events in the San Joaquin Valley.