A 42-year-old Chinese woman developed 3 weeks of swinging fever, rash, malaise, and discomfort at the right upper quadrant of the abdomen. Acute Clonorchis sinensis infection eventually became evident and the patient responded to praziquantel. Although acute infestation is usually asymptomatic, occasional cases suffer severe symptoms and present difficulties in clinical diagnosis. Clonorchiasis is endemic in South East Asia. With the increasing popularity of travel to these countries and the global migration of Asians, physicians need to be aware of the condition. Treatment with praziquantel is effective and prevents the serious sequelae of chronic infection.