This paper reports the results of a spacing experiment with bulbs of onion (Allium cepaL.) where production of seed was considered. Four spacings were compared in a line, i.e., a) 40 cm; b) 30 cm; c) 20 cm and d) 10 cm. The spacing of 10 cm between bulbs showed to be superior to the others in seed production by area. Some other advantages of this spacing are that less space is needed for the same number of bulbs to be planted and that less expenses are incurred in fertilizers, irrigation water and workmanship.