Mitchell, Scott, and Mitchell (1977) referred to near universal omission of the appropriate noncontingency poisoned sham injected control in long-delay taste aversion experiments. Examples cited were papers by Garcia, Ervin, and Koelling (1966), Revusky (1968), and Smith and Roll (1967). In defense, I pointed out that each of these papers contained both types of controls (Revusky, 1977). In a reply, Mitchell (1977) did not deny that each paper contains sham controls, but insisted that none of them contains adequate noncontingent poisoned controls. According to Mitchell, when animals poisoned some hours after consuming the CS do not subsequently avoid it, Revusky calls them noncontingent poisoned controls, but when similarly treated animals avoid the CS, they constitute an experimental group which has formed an association over a long delay (Revusky, 1968). I was not so arbitrary. I had pointed to failures by Garda et al. (1966) and by Smith and Roll (1967) to obtain aversions at their longest delays ofpoisoning as controls for aversions obtained with shorter delays in those same experiments. These are proper noncontingent poisoning controls because they control for the possibility that the taste aversions are unrelated to the contingency between the taste and the poisoning. When longer delays of sickness do not produce an aversion, the aversions obtained with shorter delays must be due to the contingency of the taste with the sickness. Such controls are excellent because all groups are equated with respect to familiarity with the test solution, history with the comparison solution (if a two-choice test is used), and experience with sickness. Furthermore, in all the experiments questioned by Mitchell, orderly delay gradients supplied further evidence that the aversions depended upon the contingency between the taste and the sickness. An analysis of the experiment by Mitchell et al. (1977) shows that the controls Mitchell considers adequate are far inferior to the controls he has criticized. Table 1 designates each group in the experiment by whether saccharin solution (Sac) unflavored water (H20) was consumed during a training trial and by whether immediate sickness (25 mg/kg of cyclophosamide), delayed sickness (by 6 h), placebo injection followed. The second column contains preferences obtained for saccharin solution (relative to unflavored water) on test Day I for each group and is based on raw data kindly supplied to me by Mitchell. The last four columns indicate determinants of saccharin preference which must be considered in any study of taste aversion learning; a yes means the indicated factor is applicable to the indicated group and a or means its effect is to increase decrease saccharin preference. Table 1 shows that the two planned experimental groups, Sac-vlmmedbick and Sac-DelaySick, are not properly equated with any of the remaining groups with respect to extraneous determinants of saccharin preference as follows. Familiarity with saccharin. The groups that drank saccharin solution during training are designated for this factor because familiarity with a flavor increases the preference for it (Revusky & Garcia, 1970). This is confirmed by the higher saccharin preference of Group Sac-Placebo than Group H20-Placebo!: t(20) = 6.56, p < .001. Mitchell's planned noncontingent poisoning control groups, H20-lmmedSick and H20-DelaySick, are not equated with his planned experimental groups, Sac-r lmmed'Sick and Sac-vDelayxlck, on this factor. Learned H20 aversion. Rats readly learn aversions to unflavored water (Elkins, 1974; Garcia & Koelling, 1967; Revusky & Parker, 1976). Group H20-lmmedSick is designated + for this factor because such an aversion was likely to increase its relative preference for saccharin solution during the twochoice test in which the alternative was unflavored water; this is marginally confirmed by its higher preference for saccharin than Group H20-DelaySick, which was equated with it on everything but delay of sickness: t(20) = 2.08, .05 < P < .06, two tails. Failure to control for an aversion to unflavored