Protoplasts from mesophyll cells of rapeseed plants (Brassica napus L. cv. Zephyr) and cell cultures of soybean (Glycine max (L.) Merr. cv. Mandarin) were induced to fuse and form heterokaryons by using polyethylene glycol. Plastids served as markers to identify heteroplasmic fusion products: the heterokaryons shared the chloroplasts from rapeseed and dense cytoplasm and colorless plastids from the soybean protoplasts. About 19–20% of the total population of viable protoplasts were identified as heterokaryons, some of which divided and formed colonies consisting of up to 10 cells within 10–12 days of culturing.