Apart from the scarcities and famines that afflicted its people, Bihar witnessed the repeated strikes of severe epidemics of cholera, smallpox, and fever during colonial rule. It also experienced a time of tribulation and affliction caused by kala-azar. Despite kala-azar being known as Dumdum fever, malarial cachexia, chronic malaria, catchetic fever, and so on, the people of Bihar called it kala-dukh (black sorrow), perhaps because of the severe sufferings it brought about, as the Garos called the disease kala-hazar and the Bengalis kala-jwar. The disease spread rapidly from the early twentieth century, which is said to have been facilitated by the continuous movement of people from Bihar to the plantation areas of Assam and Bengal. Bihar increasingly went on acquainting itself with medical intervention from the colonial health administration. Unfortunately, sources of the medical history of Bihar testify that kala-azar kept on attacking people till the end of colonial rule, and question is thus raised about the effectiveness of anti-kala-azar measures. This chapter is devoted to studying the occurrence of kala-azar in Bihar and the extent of its proliferation and containment. It aims to examine the causes of the occurrence of this disease combined with its perilous effects on people. I have tried to unearth, in the chapter, how and why kala-azar broke out there and caused ‘black sorrow’, the usefulness of anti-kala-azar measures, and the extent of the success of these measures in the containment of the disease.