The damping and strength of relaxation oscillations in BH long-wavelength lasers have been investigated. In addition to previously published papers, the relative contribution of carrier diffusion effects and spontaneous emission is analysed. At moderate pumping rates, the calculated damping factor, using singlemode rate equations and a constant spontaneous carrier lifetime, is found to be in good agreement with experimental results if the finite rise time of the pulse generator is introduced. It is also shown that the overshoot depends mainly on the spontaneous emission factor. However, in general, for the calculated spontaneous emission factor, the predicted overshoot is greater than the measured one. Possible reasons for this disagreement are discussed.