A beneficial decoloration effect resulted for horse mackerel mince washed with ozonized water within 10–20 min, but a longer washing time was required to improve the color properties when cold water or alkaline solution was used. Increase in pH as well as improvements in gel-forming ability occurred for mince washed with alkaline solution. The maximal gel strength of surimi was found when washed for 90 min. A marked decrease in pH and an undesirable gel strength of mince, as well as oxidation of the fish oil occurred during ozone treatment. Since the salt-soluble protein concentration increased for all minces washed with the three methods, improvement in gel-forming ability of washed mince was attributed to the increase in pH rather than to oil removal.