The poster describes results of experiments using a novel exposure chamber which exposes biological cells to RF radiation similar to that emitted by mobile telephones, whilst using laser scanning confocal microscope imaging. Human lymphocytes were kept within ±0.5°C of 37°C, allowing for the investigation of possible RF athermal effects. These cells were loaded with a fluorescent probe specific for calcium ions, and were monitored over two 10 minute periods. Five different conditions for cell exposure were investigated. Both continuous wave 900MHz and 217Hz pulse modulated 900MHz wave exposures were carried out on cells that were either unactivated, or alternatively activated by the mitogen phytohaemaglutinin (PHA). For these 4 conditions the average Specific Absorption Rate (SAR) was estimated to be 2W/Kg. A group of unactivated cells were also exposed to continuous wave 900MHz energy with an SAR of 10W/Kg. Results showed substantially no significant changes in calcium ion levels or signalling patterns between RF exposed and sham-exposed cells.