This Technical Report presents the sampling theory which h s resulted in the definition of the sampling plan described in ISO 8634 . The sampling plan is applicable to a large delivery of more than 250 t of fertilizer supplied to another Party, for resale, on his own responsibility, in small lots, each of which would be subject to legislation. By large amount is understood, for example, a full boat-load (5,000 t, 10,000 t or more) thus corresponding to a relatively long period of manufacture, but the theory applies to any delivery of 250 t or more.