Despite the importance of proteases in regulating plant development and protein metabolism, there are few reports describing potato protease genes. To have a global view of the expression of these genes in immature tubers, we generated expressed sequence tags (EST) through sequencing random clones in a cDNA library from immature potato tubers. Based on BLAST search homology against the recent release of GenBank, five protease gene sequences were identified from 950 high quality ESTs. Among the five, two are plastid aspartic proteases, two are cysteine proteases, and one is an ATP-dependent protease. The results indicated that multiple types of proteases are expressed with relatively high expression for cysteine protease and aspartic proteinase, but none is clearly predominant, in potato immature tubers.