Onion seed production in the northeast Brazil has been tested under experimental conditions by using artificially vernalized bulbs planted under microclimates of altitude where the low temperatures prometes desirable flowering. The idea of using the Sub-Médio São Francisco region for onion seed production has not been considered viable, since even with vernalization of the bulbs, high temperature reached under field conditions could revert the vernalization effect. In tlie present study, the technical coeffïcients of onion seed production, cultivar Composto Baia, were evaluated, under the semi-arid tropics conditions by using the vernalization system of the bulbs before planting. The results obtained under commercial scale indicate the potentiality for onion seed production under two irrigation systems ? sprinkler and furrow. Onion seed production would allow a rational utilization of the existing irrigation system as well as of the suitable dry climate essential to obtain high quality seeds.