A micro-flow system comprised of a fused-silica capillary and chemiluminescence detection was developed, in which a wide-bore hydrodynamic chromatography mode was first introduced into the system. The micro-flow system was run with a gravity method or pump now method for feeding a carrier solution into the capillary. Oxalate-hydrogen peroxide chemiluminescence reaction was adopted as a detection technique. Fluorescent compound fluorescein isothiocyanate; FITC) and FluoSphere fluorescent polymer particles with particle diameters of 0.02 mu m and 1.0 mu m were used as model samples in the present system. FITC and FluoSpheres (0.02 mu m) with diffusion indexes greater than ca. 1 were delivered into the capillary with average linear velocities under laminar flow conditions, which led to a Gaussian peak on the chemiluminescence profile. On the other hand, FluoSpheres (1.0 mu m) with a diffusion index of ca. 0.1 were delivered with the approximately maximum linear velocity and formed a non-Gaussian peak. The mixtures, FITC and FluoSpheres (1.0 mu m) as well as FluoSpheres (0.02 mu m) and FluoSpheres (1.0 mu m), renected the individual diffusion indexes, indicating two main peaks on the chemiluminescence profiles. An unexpected small Gaussian peak observed with the FluoSpheres (1.0 mu m) sample was also observed.