We present a new experimental setup for single molecule spectroscopy using a high efficient mirror arrangement with a geometrical efficiency of 0.77. Signal-to-noise (S/N) ratios up to 90 for single pentacene molecules in ap-terphenyl crystal demonstrate that increasing the detection efficiency improves the S/N ratio if the detection geometry ensures a strong stray light suppression. This is realized by the presented mirror arrangement. The experiments were done in a He contact gas cryostat, which is able to work below the lambda point. Temperatures down to 1.7 K at the sample were obtained. ©1997 American Institute of Physics.