Peyote Cactus is a small, spineless cactus, (Lophophora williamsii), whose principal active ingredient is the hallucinogen mescaline. From earliest recorded time, peyote has been used by natives in northern Mexico and the southwestern United States as a part of traditional religious rites. Mescaline can be extracted from peyote or produced synthetically. Its crown, or 'button', is used for psychedelic purposes. It is cut from the cactus and dried into a hard brown disc. The disc, sometimes referred to as a 'mescal button', contains a methoxylated amphetamine.

There are a number of cacti that are used for their hallucinogenic properties. The most common is the Peyote Cactus, found from central Mexico to southern Texas. Peyote contains relatively large quantities (one to six per cent of the plant's weight) of mescaline - a strong hallucinogen. Other cacti include the San Pedro cactus (Trichocereus pachanoi), from around the Andes, Doñana (Coryphantha macromeris) from northern Mexico and three related mescaline-bearing species from South America.

Hallucinogenic cacti are quite rare in the UK, though the peyote cactus can be bought mail order or directly from some cacti-specialists or head shops. Hallucinogenic cacti are not illegal in the UK, unless prepared for consumption as a hallucinogen. This could include drying them, or cutting them into edible 'buttons'. It usually takes six to ten of these buttons to gain the desired effect.

The peyote experience is different from that of pure mescaline - the former experience more intense and complex. This is due to the presence of many more alkaloids that affect mind and body such as hordenine, pellotine, anhalinine, anhalonine and tyramine. Some of these chemicals in combination apparently potentiate the effects of the mescaline and definitely alter some of the characteristics of the experience.