Methyl ethyl ketone peroxide (MEKP) is an organic peroxide, a high explosive similar to acetone peroxide. MEKP is a colorless, oily liquid whereas acetone peroxide is a white powder at STP; MEKP is slightly less sensitive to shock and temperature, and more stable in storage. Depending on the experimental conditions, several different adducts of methyl ethyl ketone and hydrogen peroxide are known. The first to be reported was a cyclic dimer, C₈H₁₆O₄, in 1906. Later studies found that a linear dimer is the most prevalent in the mixture of products typically obtained, and this is the form that is typically quoted in the commercially available material from chemical supply companies.