We have previously reported that chloroform is a very potent stimulator of rat hepatic Ornithine Decarboxylase (ODC) activity. At that time we conducted the obligatory time course and dose response studies in male and female rats. However, in an attempt to more thoroughly understand the mechanism of this stimulation, we have examined the effects of a series of pharmacologic, physiologic and toxicologic manipulations on the chloroform response. These studies involved: in vivo experiments in which animals were pretreated with compounds known to effect the various physiological systems and then challenged with chloroform and in vitro experiments in which chloroform was added to the incubation media with/without the compound of interest. The results did not allow the assignment of a specific effect of any of the manipulations to the mechanism of the chloroform response, although much data of significant interest evolved.