The influence of planting density on yield, growth and fruit characteristics in 'Arbequina' olive trees in Catalonia (Spain), with different plantation densities (179, 220, 227, 280, 312, and 385 olive trees/ha), was evaluated after the first 10 harvests, 1987-1996. Trees under non-irrigated conditions were planted in 1984. It was observed that, within the spacing range studied, the average olive production per hectare increased proportionally with the planting density. For the 6 studied densities the average yield obtained was higher than 5,000 kg/ha when full production (more than 6 years old) was reached. The increase in density resulted in a greater volume of canopy and external productive surface, and a higher cumulated yield per hectare. The density of 312 trees/ha (8x4 m) gave the highest economic return. So far, the plantation densities had low influence on the oil content and fruit characteristics.