The effects of two types of mands on participants' adherence to instructions were examined across two groups using procedures based on Hackenberg and Joker ("Journal of the Experimental Analysis of Behavior" 62:367-383, 1994). Participants were presented with instructions describing a pattern of responding for producing points later exchanged for money and were exposed to choice trials in which a progressive-time (PT) and a fixed-time (FT) schedule were concurrently available. The instructions initially described how to optimize point production; however, the PT schedule was manipulated over the course of the experiment such that response patterns maximizing point production differed across conditions. All participants experienced the same experimental arrangement, and the two groups differed only in the form of the mand contained in the instructions presented to them. The instructions for the directive group contained the mand "you must…" (i.e., command) preceding the instructed response pattern, whereas the non-directive group instructions contained the mand "you might consider…" (i.e., suggestion) preceding the instructed response pattern. Results indicated that instruction type influenced response patterns across changing contingencies. The directive group exhibited greater adherence to the instruction than the non-directive group when instruction following was less profitable. Results are interpreted in terms of Skinner's analysis of verbal behavior, and implications for practical application are discussed.