A microfluidic device has been developed which allows cells to be infected at many different concentrations of virus within a microscale environment. Diffusion and laminar flow were used to create a concentration gradient of virus particles over cells attached to the bottom of a microchannel. The expression of green fluorescent protein (GFP) was monitored optically in situ over several days. In characterizing non-gradient infection at the microscale, average multiplicity of infections (MOIs) ranging from 8 to 25 were used and reduced GFP expression levels, compared to accepted macroscale values, were observed. Cells infected with virus gradients also displayed reduced expression levels but their location within the microchannel followed the same trend as the virus gradient.