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Members of the family Cyperaceae were surveyed by original observation and from the literature to assess the distribution of C3 and C4 photosynthetic pathways in the family. All 107 genera were included in the current sample, with 91 genera assessed as consistently C3 and 11 genera as C4. The genera Abildgaardia, Cyperus, Eleocharis, Fimbristylis, and Rhynchospora are variable for this trait. Of the total number (1474) of specific (1406) and infraspecific (68) taxa sampled, 938 taxa (63%) are C3, 527 taxa (36%) are C4, and nine species of Eleocharis are debatably intermediate or variable in pathway. Some data suggesting further infrageneric variation in photosynthetic pathways are discussed. The ‘‘one cell distant criterion’’ accurately predicts C4 pathway in sedges, except in Eleocharis. Distribution and variability of photosynthetic pathways in Eleocharis are discussed. Photosynthetic pathway was found to be a useful taxonomic marker in Cyperaceae, despite variability in this trait at various taxonomic levels and the apparently multiple origin of C4 photosynthesis within the family. A checklist of 3395 records of C3 and C4 sedges is presented.