Toxic hepatitis occurs usually within 2-4 weeks after exposure. stress or work overloads have abruptly increased especially after the economic crisis in 1998. After the year 2000, musculoskeletal disorders became a major problem especially in assembly lines in the manufacturing industry and they were expanded to the service industry. Mental diseases related to job stress have increased. Infectious diseases increased in health care workers and afforestation workers. Occupational cancers are increasing because of their long latency, although the use of carcinogenic substances are reduced, limited, and even banned. Keywords:Occupational Diseases, Korea, Compensation, Pneumoconiosis, Asthma, Solvents, Poisoning, Cancer, Cardiovascular Diseases, Musculoskeletal Diseases == INTRODUCTION == Korea started its industrialization since the 1960s and many manufacturing factories were constructed in the 1970s and 1980s. Coal mining increased exponentially to supply the energy to the manufacturing industry and as a home heating source. Various kinds of chemicals have been used in the manufacturing industry. The traditional agriculture has rapidly decreased. Consequently, the transition toward the manufacturing industry led to many traditional occupational diseases such as carbon disulfide and heavy metal poisoning. When the industrialization began, a legal system for workers’ compensation was introduced as the first in the Korean social security system. Occupational diseases are covered by the workers’ compensation system; however, the system still can miss many unclaimed or unrecognized cases. The Korea Workers’ Compensation and Welfare Service (COMWEL) is a government-affiliated organization responsible for workers’ compensation under the Industrial Accident Compensation Insurance (IACI) Act. COMWEL requests the Occupational Safety and Health Research Institute (OSHRI) of the Korea Occupational Safety and Health Agency (KOSHA) to investigate new cases of occupational diseases if there is no clear link between the disease and work. The Ministry of Employment and Labor (MOEL) asks OSHRI to investigate cases of occupational disease if they are new and socially important. OSHRI is also legally supported to investigate workplaces if it is deemed necessary for prevention; as a result, OSHRI examines most new cases of occupational disease in Korea (1). In this article, authors will discuss the concept of occupational disease and the data resources. We will also describe occupational diseases in Korea based on the review of the cases that OSHRI has investigated, and will add more information from papers published in journals. == DEFINITON AND CLASSIFICATION == == Definition of an occupational disease == An occupational disease can be defined as a disease which arises from work or is aggravated by work. The International Labor Organization (ILO) defines occupational disease as a disease contracted as a result of an exposure to risk factors arising from work activity (2). The World Health Organization (WHO) states that an occupational disease is not characterized merely by the disease itself, but by a combination of a disease and an exposure, as well MLR 1023 as an association between the two parts (3). The term occupational disease can be academic, MLR 1023 which means that an occupational disease is defined regardless of compensation. However, the term occupational disease generally means a disease arising from work that is to be compensated through insurance or a fund contributed to by the employers. The extent of the compensation relies on the coverage of workers’ compensation insurance. In Korea, only paid employees are subject to compensation for occupational disease under the term of ‘disease due to business’ with IACI Act. == Classification of occupational disease == An occupational disease is usually compensated through Workers’ Compensation Insurance or Social Security Fund in most countries because employers are responsible for such occurrence. Conditions Nog for compensation are different in each country that MLR 1023 may exceed the list of 106 occupational diseases with 4 categories by the ILO Recommendation 194 adopted in 2002 and amended in 2010 2010 (4). MLR 1023 Korea compensates occupational diseases MLR 1023 as ‘disease due to business’ that includes cerebro-cardiovascular diseases (CVDs);.