The number of illegal cannabis plantations in Belgium has risen tremendously over the last few years. Most are small-scale, but the number of larger plantations is rising. The present proposal addressed the express need formulated by the Belgian government to quantify the yield/production capacity of illegal cannabis plantations in order to confirm/validate data from a Dutch reference study into the Belgian context. The latter study, although a landmark in itself, has a few shortcomings: it is based on data from 86 seizures whereby 'yield' was estimated as moment of seizure - this does not, however, cover previous harvests /full production and thus only gives a fragmentary idea of what the yield potential can be (from extrapolations). The study rightly considers planting density and light intensity as steering parameters influencing yield, but does not take into account the all-important variety factor. Northern Light, White Widow, Orange Bud and Jack Herrer are 4 examples of varieties currently grown, whereby it has been documented that the latter has 'high yield potential'. Lastly, the Dutch study doesn't take into account recent changes in cropping practices (change from pot soil to hydro-culture) which have modified yield/production. In order to cover for these shortcomings, the present proposal will use a regular crop experiment design, combining a number of parameters that are known to influence crop yield potential (light x planting medium x plant density x varieties) in a setting that mimicks illegal planting conditions as much as possible. As 'hard' scientific information on illegal cannabis cropping is currently unavailable, we have used the informal information available via internet to guide us in experimental design elaboration. Apart from the fact this is the only source of 'reliable' information, it is also the only source of information used by illegal growers, thus allowing us to mimick real situation conditions.