Five underground drip irrigation systems with varied, emitter spacings were evaluated for alfalfa seed production in the Imperial Valley. Previously, higher seed yields had been produced with a 50-centibar soil water tension at 9 inches below surface drip lines than with soil water tensions of 10, 100, and 200 centibars (see California Apiculture, November 1975). Since surface drip lines are subject to sunlight and mechanical damage, we began an evaluation of five underground drip irrigation systems for alfalfa seed production in November 1973 at the Imperial Valley Conservation Research Center near Brawley. The five systems with indicated emitter spacings were: (1) Chapin, continuous (a biwall system with orifices spaced 32 inches on the inside tube and water seeping through a nylon-sewn seam on the outside tube); (2) Chapin, 8.”; (3) Watersaver, 24”; (4) Nelco, 24”; and (5) Anjac, 36”. The main objective was to determine the effect of emitter spacings on alfalfa seed yield rather than to compare commercially available drip lines.