In the Morris Water Maze test, high-peak-power pulsed microwave (MW)-exposed rats displayed some learning and memory behavior dysfunctions, and their escape time and swimming distance to the submerged platform were longer than those of the sham-exposed rats. To understand the molecular mechanism involved, the reverse tran- scription-polymerase chain reaction (RT-PCR) and the Western-blotting technique were used for investigating the mRNA and protein expression patterns of the histamine H3 receptor (H3R) in rat hippocampus. High-peak-power pulsed microwave-exposure did not remarkably lead to the change in expression of H3R mRNA in rat hippocampi; however, it promoted the up-regulatory expression of the H3R protein, which was possibly triggered through the mi- togen-activated protein kinase (MAPK) pathways. Therefore, further investigation of the molecular mechanism of the MW effects on the learning and memory behaviors is required. In the Morris Water Maze test, high-peak-power pulsed microwave (MW) -exposed rats displayed some learning and memory behavior dysfunctions, and their escape time and swimming distance to the submerged platform were longer than those of the sham-exposed rats. To understand the molecular mechanism involved, the reverse trancription-polymerase chain reaction (RT-PCR) and the Western-blotting techniques were used for investigating the mRNA and protein expression patterns of the histamine H3 receptor (H3R) in rat hippocampus. -peak-power pulsed microwave-exposure did not remarkably lead to the change in expression of H3R mRNA in rat hippocampi; however, it promoted the up-regulatory expression of the H3R protein, which was potentially triggered through the mi- togen-activated protein Therefore, further investigation of the molecular mechanism of the MW effects on the learning and memory behaviors is required.