Extremes in fearful temperament have long been associated with later psychopathology and risk pathways. Whereas fearful children are inhibited and anxious and avoid novel events, fearless individuals are disinhibited and more likely to engage in aggressive behavior. However, very few studies have examined fear in infants from a multimethod and prospective longitudinal perspective. This study had the following objectives: to examine behavioral, maternal reported, and physiological indices of fearful temperament in infancy, together with their relations and stability over time; and to establish whether early indices of fear predict fear later in toddlerhood. We also examined the association between behavioral and physiological measures of fear and guilt and whether fear in infancy predicts guilt in toddlers. Finally, we investigated infant risk factors for later psychopathology. We recorded skin conductance level (SCL) and heart rate (HR) and observed children's responses during a Laboratory Temperament Assessment Battery fear paradigm across the first 3 years of life and during a guilt induction procedure at age 3 (N = 70). The results indicate that different measures of infant fear were associated across time. Observed fearlessness in infancy predicted observed fearlessness and low levels of SCL arousal to fear and guilt in toddlers. Low levels of HR and SCL to fear in infancy predicted low levels of physiological arousal to the same situation and to guilt 2 years later. Fear and guilt were significantly associated across measures. Finally, toddlers with clinically significant internalizing problems at age 3 were already notably more fearful in Year 1 as reflected by their significantly higher HR levels. The results indicated that assessments of children in infancy are predictive of how these children react 2 years later and therefore lend support to the idea that the emotional thermostat is set in the first 3 years of life. They also showed, for the first time, that infant fear is a predictor of guilt, which is an emotion that develops later. The implications of these findings for our understanding of developmental psychopathology are discussed.