Chronic pancreatitis (CP) has been considered an intractable inflammatory disease that is progressive and irreversible after definite structural changes appear in the pancreas. The Japanese diagnostic criteria for CP were revised in 2009. One of the reasons for this revision was to define a diagnostic criterion for the early phase of CP (early CP) to improve a patient's clinical outcome, because the disease progression might be reversed in this phase by a therapeutic intervention. However, the clinical features and outcome of early CP remain largely unknown, and the diagnostic reliability of early CP needs to be verified. Here, we show two patients who met the diagnostic criteria of early CP and then progressed to the advanced, late phase of CP (definite CP). A 64-year-old man with recurrent acute pancreatitis was diagnosed as early CP and later progressed to definite CP with multiple pancreatic calcifications at the age of 69. The etiology of CP in this patient was thought to be idiopathic. The other patient was a 57-year-old man with alcohol abuse (ethanol consumption > 120 g/day). He was diagnosed as early CP and then rapidly progressed to definite CP without any acute attack. He could not remain abstinent after the diagnosis of early CP. In the present report, we retrospectively demonstrated distinct clinical features of the two patients, both of whom were diagnosed as early CP first and then progressed to definite CP. Thus, our findings support the disease concept of early CP and also suggest the validity of the revised Japanese criteria for the diagnosis of early CP.