Hashish consists of the tetrahydrocannabinol-rich resinous bulbs known as trichomes as well as other minute plant material from the male and/or female flowers of the cannabis plant. It is separated from the plant via various sieving methods, cold-water extraction, or chemical extraction. The resulting plant material is known as kif (aka keef). The kif is compressed into blocks which are easily stored and transported, without degrading the THC content due to oxidation. Pieces are then broken off, warmed up and sometimes mixed with tobacco or marijuana, and smoked in water pipes, joints or hookahs. Since THC is fat-soluble, it is also possible to dissolve hashish in butter used for cooking. The Middle East and North Africa and in particular Morocco, Pakistan, and Afghanistan are the main sources of hashish, although the science of hash extraction and the rapid dissemination of this knowledge means that more and more people are making hashish for personal use, using readily available materials or custom built devices such as Bubble Bags.

Black hash, which is generally produced in Nepal, Afghanistan, and India, generally produces a more relaxing, mellow effect. Blonde hash, often from Morocco and the Netherlands, tends to produce more active and cerebral highs.

Hashish is widely available in Europe, as opposed to Marijuana which is more sparsely available on the whole. This is probably because hashish much more compact, and thus much easier to smuggle than Marijuana. Blocks of 100, 125, 200 and 250 grams of hash are common. In some places a block is dissolved, mixed with a foreign material without psychoactive or intoxicating properties, and re-pressed into a hashish block, which is sold as if it was the pure product. This is known as Soap, probably as soap is a commonly suspected additive.

Pure, properly stored hashish of premium quality is soft and moldable by the heat of the fingers alone. Old, improperly stored hashish of poor quality is rock hard and brittle, and has to be heated substantially before it becomes soft enough for use. Most hashish falls in between these two extremes, and the tactile qualities also vary according to the methods used in extraction and pressing.

Many believe that the word assassin derives from the Arabic word Hashshashin, an Islamic sect of militants who supposedly were avid hash-eaters; however, there are those that disagree, since the effects the Hashshashin reported are not generally experienced by people who consume hash [1].

The THC content of hashish that reached the United States, where demand is limited, averaged 6 percent in the 1990s. The marijuana at the CannaTrade 2002 had THC levels ranging between 8 percent and 28 percent; the latter is comparable to some grades of hashish. Note that higher levels of THC do not necessarily imply higher levels of THC consumption, as users will frequently self-titrate (at least when smoking or using a vapouriser), consuming only the desired effect is reached; admittedly, though, it is easier to overdo with more potent material. However, when it is practiced effectively, higher-THC material is healthier to consume, since fewer tars and particulates are inhaled to get the same high.