Cloning the gene encoding a dipeptide transporter is necessary for understanding the absorption mechanism of peptides and peptide-like drugs in the gastrointestinal tract. Functional expression of a dipeptide transporter after microinjection into Xenopus laevis oocytes was performed using the mRNA purified from human intestinal HT-29 cells. Fifty nanoliters of purified mRNA (1 mg/mL) were microinjected into healthy oocytes followed by incubation for 4 days in order to express a dipeptide transporter. Functional expression was determined by a uptake assay using 10 Ci/mL $[^3H]-glycylsarcosine$, a dipeptide substate of the transporter. Seasonal variability and batch-to-batch variability were greater in summer. The usage of beveled micropipettes improves viability of oocytes at 4 days after microinjection. Expression of a dipeptide transporter in oocytes after microinjection of mRNA obtained from HT-29 cells was significantly larger than those after microinjection of water or mRNA obtained from the rabbit intestine.