The neonicotinoids, a class of insecticides of relatively recent concept, have been used since the '80s for the interesting effects that they could have being systemic and long lasting. However these active ingredients manifested also a high toxicity to pollinating insects, particularly against the honey bee, causing numerous secondary effects, often not easily identifiable, such as behavioural disturbances, impaired orientation, impairment of social activities, etc... In recent years there have been alarming phenomena of bee mortality, due, in some cases, to the use of neonicotinoids as tanning agents and as pesticides. It was therefore considered appropriate to test in the laboratory the toxicity of Imidacloprid, Clothianidin and Thiametoxam on different strains of Apis mellifera to verify a greater or lesser sensitivity to the three active ingredients. To this end, using the method developed at the DI.VA.P.R.A., commercial products were used. They were tested initially at the concentrations recommended for field treatments. Where observed mortality of the treated bees was higher than that found for the untreated control, decreasing concentrations were tested down to concentrations which had no longer significant differences compared to the controls. Observations and films were made during the experiment. The bees that died during the experiment were collected and analyzed to detect the amount of active ingredient detectable; such amounts resulted much lower that administered quantities.