The variation of the principal characteristics of the mercury visible triplet self‐reversed lines is studied as a function of radial and temporal profiles of the temperature and of the species densities in high pressure mercury discharges (∼2 and ∼3 atm) operating on 50 Hz ac. An investigation is made into the effect of different theoretical and experimental parameters on the shape of calculated self‐reversed lines. By comparison between experimental and theoretical results an estimation is made of the broadening constants and of the transition probabilities of the lines.