A new neuronal model of classical conditioning is proposed. The model, called the delay-producing connections (or DPC) model, is an extension of Klopf's (1988) drive-reinforcement model and Sutton and Barto's (1981) model. The DPC model makes two contributions: lt represents the trace of each conditioned stimulus (CS) by a differential equation; and it replaces each CS in the activation rule by its CS trace, which is assumed to be equal to the CS eligibility. The DPC model reproduces the usual shape of a conditioned response, the curve of efficacy of conditioning as a function of the interstimulus interval (ISI), the dependence of the optimal ISI on CS duration, the extinction of a conditioned response [even for long-lasting CSs as opposed to Klopf's (1988) model], and several other properties of classical conditioning.