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A 2-year whole-farm study compared pasture-based systems increasing milk production per ha by increasing either stocking rate (from 2·5 to 3·8 cows/ha) or milk yield per cow (from 6000 to 9000 kg/ cow/ lactation) or both. Four treatments (systems), comprising 30 cows each, were compared under the same management and grazing decision rules. The diet was based on grazed pasture, whereas pellets and conserved fodder were fed when deemed necessary. Milk production per ha increased by 0·49, 0·1 and 0·66 in the systems that increased either stocking rate, milk yield per cow or both respectively. Cows in the ‘high milk yield per cow’ systems had a significantly higher body condition score throughout the lactation, but reproductive performance was similar among all groups. Total pasture utilized (11 t DM/ ha/ year) and pasture nutritive value were similar across all systems. This was associated with the grazing rules applied and the ability of accurately supplementing to meet deficits in available pasture. At the whole-system level, there was a higher marginal efficiency of supplement use when increasing stocking rate than when increasing milk yield per cow or increasing both (0·18, 0·07 and 0·12 kg milk/ MJ of metabolizable energy of supplements respectively).