Heavy cigarette smokers individually attended daily 3-h test sessions which were run in specially designed cigarette smoking evaluation rooms. Subjects were required to use the cigarette holder provided, and were required to extinguish each cigarette 4 min after the first puff on the cigarette. Other than these restrictions, subjects were allowed to smoke ad libitum. The concentration of delivered tobacco product was varied from 100 to 10% across sessions by using graded commercially available ventilated cigarette holders. As concentration of tobacco product was decreased, rate of puffing and total number of puffs showed robust compensatory increases. Number of cigarettes increased only moderately in response to decreases in tobacco product concentration. There was little change in subjective ratings of strength on smoking satisfaction. Finally, expired air carbon monoxide (CO) values and cigarette butt weights were relatively stable across the four ventilation conditions. These later findings suggest that a significant degree of compensation had occurred in response to the concentration manipulations.