An infrared fluorescence microscope consisting of a laser diode for exciting infrared fluorophores attached to DNA oligo-nucleotides and a silicon avalanche photodiode for detecting the infrared emission has been designed. The microscope was mounted on a scanning platform which could be optimally focused on an electrophoretic gel (0.1 - 0.4 mm thick) sandwiched between two glass plates. Background fluorescence is minimal in the infrared region of the optical spectrum. In addition, the optics were designed to further minimize this background fluorescence while maximizing the signal output. A 5 pM fluorophore-DNA concentration in unpolymerized gel solution (about 2000 molecules in an irradiated volume of 600 pL) gave a signal-to-noise ratio of 4:1, 3:1, and 2:1 for a glass-gel-glass sandwich made using quartz, borosilicate, and soda-lime glass, respectively.