Marijuana with the highest THC content is typically found in strains of cannabis that have been specifically bred to produce high levels of the psychoactive compound. These strains are often referred to as high THC" or "high potency" varieties, and they can contain up to 30% THC by weight. While there are many different high THC strains available, some of the most popular include OG Kush, Granddaddy Purple, and Sour Diesel."