A disordered Kronig-Penney model of length L in an electric field F is studied. The transfer matrix approach is used to evaluate the transmission coefficient T. It is found that for F not=0, and large L, -ln T/L identical to alpha is well behaved statistically, although with a nongaussian probability law. The possible existence of a critical field above which states would be strictly extended is discussed in terms of a breakdown of a non-standard form of the central limit theorem.