K(+) channels are key molecules in the progression of several cancer types and considered to be potential targets for cancer therapy. We examined the gene expressions of voltage-gated (K(v)), Ca(2+)-activated (K(Ca)), and two-pore domain (K(2P)) K(+)-channel subtypes in needle-biopsy samples of human prostate cancer (PCa) by real-time PCR and compared them with those in PCa epithelial cell lines. The expression of K(v)1.3, K(Ca)1.1, K(Ca)3.1, and K(2P)1 markedly increased in the PCa group with Gleason score of 5 - 6 (GS5-6) but significantly decreased in the GS8-9 group. This malignancy grade-dependent K(+)-channel expression pattern may provide a convenient marker to understand PCa progression level.