Haemocystidium lygodactyli n. sp. parasitizes Lygodactylus capensis grotei (Gekkonidae) in Tanzania. Mature gametocytes in acute phase of infection average 16.3 × 5.7 μm (11–20 × 4–9.5 μm), with LW 93.0 (62–140 μm²) and L/W ratio 2.94 (1.2–3.9). Gametocytes usually lateral, lateropolar, or halteridial in position. There was no significant sexual dimorphism in gametocyte dimensions. Nuclei discrete in both sexes at maturity, with a rounded nucleolus usually present in microgametocytes. In chronic infection, gametocytes were 18.1 × 8.7 μm (8–25 × 5–11 μm), with LW 156.8 μm² (80–250) and L/W 2.16 (1.1– 3.6). When gametocytes from the chronic infection were compared with the same sex in acute infection, length did not differ, but differences were present between the same sex in each comparison of width, LW, and L/W. Macrogametocytes and microgametocytes in chronic phase were broader, larger, and less elongate and most commonly halteridial. Meronts were found only in endothelium and connective tissue of lung. Elongate to oval in shape, the larger meronts filled with nuclei were 12.2 × 6.9 μm (10.0 × 5.0–16.0 × 9.0), with LW 50–144 μm² (85.1). In 1 initial infection followed for 49 days, apparently mature gametocytes appeared by day 28 postcapture. Binucleate parasites were present from day 14 throughout the course of infection, with their frequency increasing from 5% of immature parasites to 34% of mature gametocytes. Binucleate mature gametocytes were found in 1 other infection, where 14% had 2 nuclei. Sex ratio varied from 51 to 63% in favor of macrogametocytes.