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The effects of various neem products on nymphs of Schistocerca gregaria were tested in semi-field (cage) trials in the southern Tamesna desert (Republic of Niger). The neem products applied were from different sources (Prof. SCHMUTTERER, University of Giessen, and Dr. H. KLEEBERG, Trifolio GmbH, Lahnau), and different 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 % mortality in both test populations (applied quantities: 1 l/ha), compared with mortality rates of 60-70 % for the products from Giessen (applied quantities 10 l/ha). The laboratory-reared nymphs proved to be more sensitive, i.c., these populations died 4-6 days earlier and exhibited higher rates of morphogenetic defects after application of sublethal dosages.