Chemical Weapons:
North Korea has not signed the Chemical Weapons Convention (CWC) and probably will not do so because the CWC, unlike the Biological Weapons Convention (BWC), requires international inspections of ratifying countries, and the North Koreans are not eager to disclose the extent of their chemical weapons (CW) capability.

The North Korean CW program is run by the Nuclear-Chemical Defense Bureau, created in 1981.  The majority of Korean weaponized chemical agents are mustard gas, phosgene, sarin and V-agents, though North Korea is also known to have produced quantities of soman, tabun and hydrogen cyanide, among others.  Current estimates of the North Korean stockpile range from 1,000 metric tons to the high-end estimate of 5,000 metric tons given by the South Korean government.  North Korea's CW arsenal poses a particular threat to the United States as: "In any attack on the South, North Korea could use its arsenal of chemical weapons to attack U.S. or allied forces deployed along the demilitarized zone."  The preparedness of the North Korean army to act in a contaminated theatre of war (many troops are outfitted with protective gear, CW detectors and decontamination systems) indicates that the country has not ruled out the possibility of using CBW.

Biological Weapons:
Though North Korea has been a signatory of the Biological Weapons Convention (BWC) since 1987, Pyongyang has been involved in BW related R&D for the past three decades, focusing on the pathogens anthrax, cholera and bubonic plague.