3-Methylmethcathinone, also known as 3-MMC and 3-mephedrone, is a designer drug from the substituted cathinone family. 3-MMC is closely related in structure to the more common illicit drug mephedrone (4-MMC) and is illegal in most countries that have banned mephedrone as it is a structural isomer of it. However, 3-MMC has still appeared on the recreational drug market as an alternative to mephedrone and was first identified as being sold in Sweden in 2012. Unlike other legal highs, 3-MMC was tested and characterized in large mammals, providing much more knowledge about it than is known about other synthetic cathinones. 3-Methylmethcathinone or 3-MMC is a monoamine transporter substrate that potently inhibits norepinephrine uptake and displays more pronounced dopaminergic vs. serotonergic activity.