The tetrahydrocannabinol (THC) content of hash oil varies tremendously, since the manufacturers use a varying assortment of marijuana plants and preparation techniques. Dealers sometimes cut hash oils with other oils. The form of the extract varies depending on the extraction process used; it may be liquid, a clear amber solid (called “shatter"), a sticky semisolid substance (called "wax"), or a brittle honeycombed solid (called "honeycomb wax").
Hash oil seized in the 1970s had a THC content ranging from 10% to 30%. The oil available on the U.S. West Coast in 1974 averaged about 15% THC. Samples seized across the United States by the Drug Enforcement Administration over an 18-year period (1980–1997) showed that THC content in hashish and hashish oil averaging 12.9% and 17.4%, respectively, did not show an increase over time. The highest THC concentrations measured were 52.9% in hashish and 47.0% in hash oil.  Hash oils in use in the 2010s had THC concentrations as high as 90% and other products achieving higher concentrations. Following an outbreak of vaping-related pulmonary illnesses and deaths in 2019, NBC News conducted tests on different black market THC vape cartridges and found cartridges containing up to 30% Vitamin E acetate, and trace amounts of fungicides and pesticides that may be harmful.
The following compounds were found in naphtha extracts of Bedrocan Dutch medical cannabis:
* Cannabinoids: THC (~ 30%) and THCA (~ 60%).
* Monoterpenes (~ 5%): β-pinene, myrcene, β-phellandrene, cis-ocimene, terpinolene, and terpineol.
* Sesquiterpenes (~ 5%): β-caryophyllene, humulene, δ-guaiene, γ-cadinene, eudesma-3,7(11)-diene, and elemene.