Mecanically shelled peanut (Arachis hypogaea L.) seeds of the cultivar tatu, with initial moisture contents of 5.2, 6.2, 7.0, 8.2, and 9.2%, and packaged in polyethylene bags of 0.05, 0.08, 0.10, and 0.15mm thick. were stored in a room with no temperature and relative humidity control, in Campinas, State of São Paulo. Germination and moisture content percentagens were determined at 3, 6, 9, 12, and 18 months storage. The initial moisture contents of 8.2 and 9.2% were damaging to the preservation of the seeds, mainly when these were packaged in the bags of 0.15 or 0.10mm thick. The best storage conditions were those provided by drying to 5.2 or 6.2% moisture levels, and packaging in 0.15 or 0.10 mm thick plastic bags. The walls of the plastic bags did not hamper moisture vapor transmission between environment and seeds. The transmission rates were higher in the bags of thinner walls.