Over the past 15 years the use of mobile phones has increased considerably, with a current estimate of more than one billion users worldwide. The Australian population represents some of the most active users, recognised by the fact that on average 4 devices are in operation among every 3 people. While the impact of these devices on human health is under active debate, the electromagnetic radiation (EMR) emitted by mobile phones has been highlighted as a possible carcinogen by the International Agency for Research on Cancer. Owing to the practice of storing mobile phone devices in the pant pocket, in line with the reproductive system, it is becoming increasingly important to assess the effect of radiofrequency-EMR (RF-EMR) on the male germ line particularly as several studies have identified a potential impact of RF-EMR on sperm function and DNA integrity. In this study, mouse germ cell lines (GC1, spermatogonial like; GC2, spermatocyte like) and cauda epididymal spermatozoa were exposed to RF-EMR generated by a waveguide for 0-6 hours. Radiation mimicking that emitted by mobile phone devices (0.15 W/kg, 1.8 GHz) induced significant increases in mitochondrial reactive oxygen species production in both GC1 (p<0.01) and GC2 (p<0.05) cell lines, after 2 and 4 hours of exposure, respectively. A similar effect was not observed in mature spermatozoa, however the motility of these cells proved particularly sensitive with significant reductions (p<0.05) recorded across the categories of rapid, progressive and total motility after 4 hours of exposure. This treatment also led to a marked suppression of sperm maturation as judged by the failure of these cells to undergo capacitation-associated increases in phosphotyrosine expression within their tail. Our continuing research will focus on the downstream effects of RF-EMR on sperm fertilising ability and determining the precise mechanism(s) underpinning the differential effects observed in developing germ cells.