In recent years, research-methods literature mainly addressing controlled clinical trials has arisen regarding explanatory and pragmatic treatment trials. Explanatory trials tend to examine causal mechanisms and questions of efficacy and value internal validity (creating optimal study conditions) over generalizability (using study results to understand treatment effects in real-life patient populations). In contrast, pragmatic trials value "external relevance" (generalizability) of study results over "internal elegance" so that clinicians and health policymakers can better understand how treatments might impact their patients and policies. This review draws inspiration from these contrasting explanatory and pragmatic perspectives and develops them for clinical and research pertaining to idiopathic physical symptoms and related syndromes (eg, somatization disorder, chronic fatigue syndrome, multiple chemical sensitivities, irritable bowel syndrome). Explanatory and pragmatic perspectives are used to examine these idiopathies with regard to causation, case definition, labels, and treatment. It is concluded that idiopathic symptom syndromes are fundamentally pragmatic clinical and research challenges. For epidemiologic and methodologic reasons, the complex explanations for these syndromes remain largely elusive. Even so, scientific and clinical pragmatism offers the opportunity to reduce disagreement between competing medical disciplines and between clinicians and affected patients with regard to irreconcilable etiologic questions and to remain evidence-based in the care of patients.