The expression of keratinocyte growth factor (KGF) messenger RNA (mRNA) was examined in both ex vivo and in vitro specimens of human skin, conjunctiva and cornea. Total cellular mRNA was extracted from human skin, conjunctiva, cornea, cultured skin fibroblasts, cultured conjunctival fibroblasts and cultured keratocytes. Oligo dT-primed complementary DNA (cDNA) was synthesized using each RNA sample as a template. Polymerase chain reaction (PCR) was used to amplify the DNA sequence of KGF using each cDNA sample as a template. PCR products were then digested with restriction enzymes in order to determine the KGF prototype. In all samples, PCR products of the expected size for KGF were detected. The resulting restriction pattern proved that these products were identical to KGF prototype I, ie, authentic KGF. In conclusion, human keratocytes and conjunctival fibroblasts express mRNA coding for KGF prototype I, ie, authentic KGF, in both ex vivo and in vitro specimens.