The stability of an azadirachtin-containing solid preparation is increased if the preparation contains about 5% or less volatile polar solvents and 1% or less water. Reduction of the percentage of volatile polar solvents present in preparations of azadirachtin-containing solids to such levels improves the storage-stability of the solids without significantly degrading the azadirachtin in the solid. Solvents are preferably removed by drying the preparation at a suitable temperature for a time sufficient to reduce the level of water and volatile polar solvents to acceptable levels.