A replica technique was developed to improve the conventional method for screening poly(3-hydroxyal-canoate) [P(3HA)]-accumulating bacterial colonies on agar plates by means of Nile blue A staining. In the conventional method the ethanolic dye solution causes damage to the colonies. This is avoided in the replica technique by transferring a portion of a colony’s cells onto a membrane, staining the membrane with a 1% Nile blue A ethanolic solution, and irradiating the dried membrane in the dark UV Light. Cells that accumulate P(3HA) exhibit blight-orange fluorescence, whereas cells that do not accumulate P(3HA) appear as dark spots. Glass fiber Biter paper was found to be the most suitable membrane material. The effectiveness of the technique was demonstrated using colonies of P(3HA)-accumulating Alcaligenes eutrophus and Alcaligenes latus.