Culturable airborne bacteria and fungi were sampled in a domestic waste transfer station in Mexico City. Close to where the waste was handled, the geometric mean concentration of bacteria was >6700 cfu/m 3 of air, of Gramnegative bacteria >460/m 3 and of fungi >4900 cfu/m 3 of which 75% were Penicillium spp. Concentrations of microorganisms downwind of the waste site were greater than upwind. Salmonella was recovered on Trypticase Soy Agar from 14% of samples. The large concentrations of Gram-negative bacteria and fungi in the waste transfer station could lead to different types of pulmonary reactions, and thus constitute a respiratory hazard to workers, and possibly also to the neighboring population.