The purpose of this study was to examine the association of prenatal exposure to cigarettes to measures of reactivity at 2 and 9 months of age. 191 9-month old infants (134 exposed, 57 nonexposed) were recruited prenatally. Cigarette exposure status was determined by a combination of maternal report, chart review, maternal salivary cotinine, and infant meconium. At 2-months, temperamental reactivity was assessed with the distress to limitations subscale of the revised Infant Behavior Questionnaire (IBQ-R; Garstein & Rothbart, 2003). Behavioral reactivity consisted of infant negative affect assessed during a mother-infant feeding interaction. Physiological reactivity was assessed with respiratory sinus arrhythmia (RSA) at the 9-month laboratory assessment during a negative affect (NA) paradigm. The NA paradigm consisted of a gentle arm restraint episode. Average RSA was calculated for baseline, and for the NA paradigm. To assess physiological reactivity, a change score for RSA from baseline to NA was calculated. Negative scores indicate a decrease in RSA and more optimal regulation during challenge. Structural Equations Modeling used to test the model indicated a significant direct association between prenatal cigarette exposure and physiological reactivity during frustration. Exposed children had a smaller decrease in RSA during the NA task indicating less optimal reactivity in response to frustration. Temperamental and behavioral reactivity at 2 months of age were also both associated with physiological reactivity at 9 months of age. Higher levels of negative affect and higher scores on the distress to limitations subscale were associated with smaller decreases in RSA