[en] We present experimental results on the two-body loss rates in a magneto-optical trap of metastable helium atoms. Absolute rates are measured in a systematic way for several laser detunings ranging from -5 to -30 MHz and at different intensities, by monitoring the decay of the trap fluorescence. The dependence of the two-body loss rate coefficient β on the excited state (2³P₂) and metastable state (2³S₁) populations is also investigated. From these results we infer a rather uniform rate constant K_sp = (1±0.4) x 10^-7 cm³/s. (orig.)