A linear image sensor combined with a microcomputer system was applied to the immunoassay for human immunoglobulin G (H-IgG) based on turbidimetry. Antibody bound latex beads (Ab-L) were reacted with H-IgG in a glass capillary (0.8mmΦ× 70mm). The light scattering intensity profilesalong the capillary were analyzed from the light intensities at each element of the image sensor. A good correlation was obtained between the normalized variation of light intensity at 15 min and the concentration of H-IgG in the range 5×10−85×10−10g.ml−1.