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Mate choice by males in organisms that do not make obviously costly contributions to offspring should be expected where sperm production is limited and courtship time is finite. Although male guppies (Poecilia reticulata) contribute only sperm to their offspring, preliminary evidence points to male mate choice in this species. Thus, the hypothesis that male guppies choose their mates was investigated. Mate choice was measured by giving males a choice of different-sized females, using only visual cues. The data revealed that males preferred large females over small females whether they were presented singly, in pairs, or with a small female. This preference may arise because large females may produce larger broods.