The feasibility of genetically engineering soybean seed coats to divert metabolism towards the production of novel biochemicals was tested. The genes phbA, phbB, phbC from Ralstonia eutropha each under the control of the seed coat peroxidase promoter were introduced into soybean and the production of polyhydroxybutyrate (PHB) was assayed. The analysis of seed coats arising from 4 independent transformation events demonstrated that PHB was produced at a mean of 0.12% seed coat dried weight with individual values up to 0.36%. These values demonstrate that it is possible to metabolically engineer soybean seed coats.