Patients are often prepared for procedural discomforts with descriptions of pain or undesirable experiences. This practice is thought to be compassionate and helpful, but there is little data on the effect of such communicative behavior. This study assesses how such descriptions affect patients' pain and anxiety during medical procedures. The interactions of patients with their healthcare providers during interventional radiological procedures were videotaped during a previously reported 3-arm prospective randomized trial assessing the efficacy of self-hypnotic relaxation. One hundred and fifty-nine videos of the standard care and attention control arms were reviewed. All statements that described painful or undesirable experiences as warning before potentially noxious stimuli or as expression of sympathy afterwards were recorded. Patients' ratings of pain and anxiety on 0-10 numerical scales (0=No Pain, No Anxiety at All and 10=Worst Pain Possible, Terrified) after the painful event and/or sympathizing statement were the basis for this study. Warning the patient in terms of pain or undesirable experiences resulted in greater pain (P<0.05) and greater anxiety (P<0.001) than not doing so. Sympathizing with the patient in such terms after a painful event did not increase reported pain, but resulted in greater anxiety (P<0.05). Contrary to common belief, warning or sympathizing using language that refers to negative experiences may not make patients feel better. This conclusion has implications for the training in medical communication skills and suggests the need for randomized trials testing different patient-practioner interactions.