While chronic illness has a profound impact upon the individual, an immense burden is imposed upon the family. When the competing demands of an illness and the family escalate exponentially, there may be a crisis. Traditionally, crisis theory has been applied to acute care contexts such as emergency, intensive care and mental health nursing. Yet, clinical experience with families and chronic illness supports the notion of periodic crises from the prediagnostic phase to the long-haul of the illness. Moreover, the authors hypothesize that the family's perception of the event determines whether the crisis is perceived as a threat or a challenge. This paper thus addresses the perception of crisis within the framework of chronic illness from a biological and family systems nursing perspective. First, the theory of Humberto Maturana, a Chilean biologist, is explored and applied to clinical observations regarding family, crisis and chronic illness. Second, an evolutionary model for conceptualizing crisis and chronic illness is presented. Third, the role of beliefs in the family perceptions of crisis and chronic illness is discussed.