Evidence from naturalistic and laboratory studies indicates that schizophrenic symptoms are exacerbated by stress or arousal of negative affect in some patients and not in others. Affective reactivity of symptoms may reflect a pathophysiological process or set of processes present only in a subset of cases of schizophrenia and, therefore, may constitute a dimension potentially relevant to subtyping efforts aimed at discriminating separate processes within the disorder. This paper reviews the evidence a) that affective reactivity of symptoms exists in some but not all schizophrenic patients, b) that this dimension corresponds with other variables that also are putative process discriminators, and c) that it is associated with a more global pathological reactivity to sensory and affective stimuli. Hypotheses as to its biological substrata, relevance to treatment, and importance to larger diagnostic issues are discussed.