[en] The effect of high hydrostatic pressure, up to 100 kbar, on the emission spectra of Cr³⁺ ions in GdAlO₃ hosts was studied. A linear shifting (red-shift) of the single-ion line (the R line), the left-hand side (LS) line, right-hand side (RS) line and the neighbouring-pair line (NPL) was observed. The R line shows a pressure-induced shift of 0.082 nm kbar^-1, nearly 2.25 times that of ruby. The LS line, RS line and NPL show pressure-induced shifts of 0.0779 nm kbar^-1, 0.0864 nm kbar^-1 and 0.0933 nm kbar^-1, respectively. (author)