Rats shifted from a 40% sucrose solution to a quinine-adulterated (30 mg/100 ml) 40% sucrose solution showed a reduction in consumption to a level considerably below that of animals exposed to only the quinine-adulterated solution. The animals tended to recover from this negative contrast effect over a 5-day postshift period and, in general, the degree of contrast was about equivalent to that of animals shifted from a 32% to a 4% sucrose solution. There were no sex differences in the rats shifted from 32% to 4% sucrose, but female rats shifted to the quinine-adulterated sucrose showed larger contrast effects than male rats exposed to the same shift.