There are several agrochemicals that manifest moderate or low harmfulness towards adult bees but, because of their negative effects on the brood, they can result in damage to the colony. Thus, it is important to have a method for testing toxic effects of such substances on bee brood. In the in vivo tests where larval development depends on nurse bees, the interpretation of results may be biased by different factors, in particular the inability to assess the exact amount of the a.i. ingested by the larvae. To avoid these problems, an innovative in vitro rearing method of honey bee larvae was devised to assess the effect on brood of any substance that can reach the hive with nectar and pollen. In this method, the tasks of nurse bees are accomplished by man. This method could be used in the risk assessment process since it meets with the following characteristics: low mortality rate in negative control, standardization of the test and easiness of carrying out, sensitiveness to treatments, precise control of the ingested doses of diet and pesticide, assessment of larval mortality for each larval instar, of prepupae weight and of adult emergence rate. The method enables the study of both the lethal effects (calculation of LD50) and the sublethal effects (prepupal weight, duration of development, adult morphology and behaviour). The method can be used either to study acute effects by applying contaminated diet to one particular instar or to investigate chronic effects by providing each day the larvae with the test substance. This rearing method was used for testing the toxicity of 2 insecticides, dimethoate considered as a reference insecticide in toxicological tests on adults and diflubenzuron which belongs to the IGR group.