The Reduction of Smoking in Cardiac Patients (ROSCAP) Study is a randomized controlled trial to test the effectiveness of a smoking reduction strategy to decrease tobacco-related harm, promote cessation, and improve biochemical and clinical indicators of toxin exposure among patients with heart disease. We analyzed baseline characteristics of patients enrolled for participation to investigate predictors of spontaneous smoking reduction prior to study enrollment. Past reducers were more likely to be males (p=.009) and had higher past peak smoking level (p<.0001) than nonreducers. Gender and number of heart disease diagnoses predicted the occurrence of spontaneous reduction and its extent. Age and a history of chronic obstructive pulmonary disease also predicted the extent of reduction. Cotinine and nicotine levels per cigarette per day were significantly higher among past spontaneous reducers than nonreducers. Spontaneous reduction is common among medically ill smokers. Past history of heart disease is a strong predictor of prior reduction. There is evidence of compensation among past spontaneous reducers.