People who experience an MI often do not realize their evolving symptoms are cardiac in origin and consequently delay in seeking treatment. Treatment-seeking delay for MI is a recalcitrant problem that increases MI morbidity and mortality. The purpose of this study was to describe post-MI patients' challenges in accurately labeling their MI symptoms. Leventhal's self-regulatory model of illness provided the study's framework; this model proposes that symptom labels and other beliefs about the meaning and implications of symptoms guide self-care behaviors, including seeking treatment. Participants had experienced a first MI and had labeled their symptoms as representing some non-cardiac cause prior to hospitalization (N = 181; 65% male). Participants were asked whether symptoms had been similar to their beliefs about MI; if not, they described how symptoms had differed from expectations. Narrative responses were recorded and transcribed verbatim. Q-sorts were used to construct a coding system for characterizing the nature of expectancy violations (eg, symptom type, severity). Independent raters then coded narratives for the presence of content; excellent interrater reliability was observed (Ks >.90). Most participants (78%) reported that symptoms differed from their beliefs about MI, with women being more likely than men to describe expectancy violations, P = .01. The most common expectancy violation was type of symptoms experienced (69%). A sizable minority (18%) said their symptoms were less incapacitating than their MI-related beliefs had led them to anticipate. Men were significantly more likely than women to report that symptoms had been less severe than expected, P = .02. This exploration of how MI symptoms diverged from participants' beliefs and expectations provides rich information for the development of interventions designed to facilitate rapid treatment seeking behavior. Results indicate that interventions should emphasize the potential range and variability of both type and severity of MI symptoms.