Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is the most common autoimmune neuropathy. The diagnosis depends on the clinical presentation with a progressive or relapsing course over at least 2 months and electrophysiological evidence of primary demyelination. Whereas typical CIDP is quite easily recognizable because virtually no other neuropathies present with both distal and proximal motor and sensory deficit, atypical CIDP, focal and multifocal variants in particular, may represent a difficult diagnostic challenge. CIDP very likely is an underdiagnosed condition as suggested also by a positive correlation between prevalence rates and sensitivity of electrophysiological criteria. Since no ‘gold standard’ diagnostic marker exists, electrophysiological criteria have been optimized to be at the same time as sensitive and as specific as possible. Additional supportive laboratory features, such as increased spinal fluid protein, MRI abnormalities of nerve segments, and in selected cases nerve biopsy lead to the correct diagnosis in the large majority of the cases. Objective clinical improvement following immune therapy is also a useful parameter to confirm the diagnosis. The pathogenesis and pathophysiology of CIDP remain poorly understood, but the available evidence for an inflammatory origin is quite convincing. Steroids, intravenous immunoglobulin (IVIG), and plasma exchange (PE) have been proven to be effective treatments. IVIG usually leads to rapid improvement, which is useful in severely disabled patients. Repeat treatment over regular time intervals for many years is often necessary. The effect of steroids is slower and the side-effect profile may be problematic, but they may induce disease remission more frequently than IVIG. An important and as of yet uncompletely resolved issue is the evaluation of long-term outcome to determine whether the disease is still active and responsive to treatment.