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The effects of various neem products on nymphs of Schistocerca gregaria were tested in field (cage) trials in the southern and western Sahara desert (Republic of Niger). Tile neem products applied had different sources (Prof. Schmutterer, University of Giessen, and Dr. H. Kleeberg, Trifolio GmbH, Lahnau), and differed with regard to both formulation and concentrations of active compounds. All products were tested either on locusts that hatched from eggs of laboratory cultures or on nymphs caught in the field. The products supplied by Trifolio caused 100 per cent mortality in both test populations (applied quantities: 1 litre per hectare), compared with mortality rates of 60-70 per cent for the products from Giessen (applied quantities 10 litres per hectare). The laboratory-reared nymphs, proved to be more sensitive, i.e., died four to six days earlier and exhibited higher rates of morphogenetic defects after application of sublethal dosages.