We report high-resolution spectroscopic observations for a sample of 38 T Tauri stars (TTS), complemented by UBVRI photometry of 13 TTS, and CCD VRI photometry for 2 visual binaries. Based on these observations and data taken from the literature, we derive lithium abundances in 53 TTS, concentrating on weak-line TTS (WTTS). The sample spans the range in spectral types from KO-M3, approximately corresponding to masses between 1.2 and 0.2 solar mass.