The paper concerns the problem of toxic emission from non-road vehicles. The paper presents the results of the investigations and analysis related to the engine operating conditions of a combine-harvester. An analysis has been performed based on which a range of the most frequently used loads and engine speeds were determined. The obtained time density characteristics (distribution of speeds and loads in time) of the engines were compared to the measurement points of the toxic emission homologation cycle. On this basis conclusions have been drawn regarding the correlation between the measurement points of the cycle and the most frequently used areas of loads and speeds of combine-harvester. Further suggestions for the investigations and analysis have also been made referring to the issue at hand. Besides, based on the obtained results certain proposals have been formed for further development of the non-road vehicles emission legislation.