Fluorescence excitation spectra of single terrylene molecules in p-terphenyl crystals were investigated at low temperatures. The line shifts due to hydrostatic pressure and external electric fields were measured, with the electric field strength oriented either parallel or perpendicular to the (k) under bar vector of the laser light. A linear Stark effect was found for most molecules, indicating local environments of low symmetry. In sites X(1) and X(3) (and XY, a photoproduct state), spectral hole burning was observed. Whereas the holes are stable in sites X(1) and XY, they decay with a time constant of some minutes in X(3) Pressure experiments were performed on the stable hole spectra in sites X(1) and XY. In weakly doped samples, holes composed of very few molecular lines were generated with halfwidths distinctly narrower than twice the homogeneous linewidth.