We determined the effects of microwave radiation and static magnetic field on the gene activity in Drosophila by measuring the dimensions of puffing the salivary gland polytene chromosomes of Drosophila melanogaster Meigen following exposure of eggs to the radiation and magnetic field. Drosophila eggs were exposed to either microwave radiation of 36.64 GHz frequency and 1 W/m² intensity for 30 s, a static magnetic field of 25 mT for 5 min, or both. The diameter of puffs was measured in squashed salivary gland preparations extracted from larvae from those eggs as they entered the prepupal stage. The puffs measured were 50CD, 63F, 71CE, 72CD (chromosome 3L) and 82EF, 83E, 93D (chromosome 3R). Results demonstrated that (a) microwave radiation exposure decreased puffing activity in puffs 63F, 71CE, and 82 EF but had no effect on puffing at 72CD, 93D and 50CD; (b) exposure to magnetic fields only did not change puff activity, but magnetic field exposure appeared to enhance the impact of microwave radiation exposure at locus 83F by decreasing puff activity; (c) puffs 63F, 71CE, and 82EF were smaller when exposed to microwave radiation and magnetic field combined than with microwave radiation alone, and; (d) no apparent changes were observed at the 93D puff after exposure to microwave radiation and the combined treatments.