Chemicals at the present time are the only means of controlling pest damage to crops on economic, efficient, and compatible grounds. Timely application, particularly over large areas or inaccessible areas, requires aircraft to apply them. Aerial agriculture is an essential industry, and growing in worldwide use. It is being used more and more in areas of the world where food is in short supply, and will be used more extensively to increase food production. Problems are associated with the use of chemicals, or more particularly, their misuse. There is an almost infinite variety of potentially valuable insecticides. Whilst the number of individual agents can become quite large, it is fortunate perhaps, that only a few types of classes of chemicals possess useful pesticidal activity. The aerial applicator's toxicological problems are mainly concerned with four classes: dinitrophenols, carbamates organochlorines, and organophosphates. It is recommended that application pilots and ground crews using these classes of pesticides should have their individual cholinesterase levels established at the start of a season for project, and monitored at intervals. Recommended lowest levels in blood and plasma are tabulated. Electromyography is also introduced in establishing a non-invasive method of measuring toxicity in the pilots and ground crews.