The wetting behavior of polypropylene meltblown microfibers by water and oil was investigated using an environmental scanning electron microscope (ESEM). Water droplets were formed on the fiber surfaces by controlling temperature and pressure in the ESEM chamber and oil drops were added onto the fibers using a microinjector mounted on the ESEM chamber. The contact angles of water and oil were measured from the ESEM micrographs. (C) 2002 Elsevier Science Ltd. All rights reserved.