Concentrations and size distributions of airborne welding fumes in work environments were measured. Samples were collected from 20 workplaces in 13 companies. In all workplaces, the stationary samplings including A-sampling and B-sampling and the personal sampling were carried out simultaneously. The fume concentration in the stationary sampling was measured with a digital dust monitor. A low volume air sampler and an Anderson cascade impactor was also used to determine the conversion factor of the values obtained by the digital dust monitor and the size distributions of the fumes. The personal exposure levels were measured with a TR sampler and a personal cascade impactor. The concentrations by the personal sampling (average: 11.3mg/m3) were much higher than those by the A-sampling (average: 0.4mg/m3 and range: 0.15-0.64mg/m3) but lower than those by the B-sampling (average: 46.8mg/m3, range: 0.66-152.8mg/m3). The mass median aerodynamic diameter (MMAD) of the stationary and the personal samplings were 2.41 microns and 0.80 microns, respectively. Fumes were observed under a scanning electron microscope. Most of the fume particles were sphere in shape but smaller fumes were aggregated and formed larger secondary particles.