We are investigating using a transmitted light configuration in our experimental confocal microscope, in order to observe highly transparent biological preparations which typically yield little or no signal in reflection. Because refractive index and thickness variations in the specimen often deflect the focused image spot off-axis in a confocal transmission configuration, we are exploring using a CCD array detector in the transmitted beam path instead of a single-pinhole detector. Our method for detecting the brightest pixel values from the CCD diffraction image is shown to give a similar two-point response to that of a confocal fixed-pinhole transmission system. We also discuss the differences between reflection and transmission confocal modes and analyze the relative imaging properties of each.