SYNOPSIS.A survey of 22 Western Painted Turtles (WPT),Chrysemys picta belliGray; 2 Map Turtles (MT),Graptemys geographicaLe Sueur; 8 False Map Turtles (FMT),Graptemys pseudogeographicaGray; 26 Illinois Mud Turtles (IMT),Kinosternon flavescens spooneriSmith; and 5 Spiny Softshell Turtles (SST),Trionyx spiniferusLe Sueur, revealed the presence of 10 species of coccidia. The species found, the shape and average length‐width dimensions (in micrometers) of their oocysts, and the respective hosts from which they were isolated were as follows:Eimeria chrysemydisDeeds&Jahn, slightly pear‐shaped (27.6 × 17.0), from 5 WPTs;Eimeria delagei marginataDeeds&Jahn, markedly pearshaped (22.1 × 17.6), from 2 WPTs, 1 MT, and 3 FMTs;Eimeria graptemydossp. n., broadly ellipsoid to subspherical (12.6 × 11.4), from 10 WPTs, 2 MTs, and 5 FMTs; Eimeria lutotestudinis sp. n., broadly ellipsoid to subspherical (11.9 × 10.8), from 4 IMTs; Eimeria mascoutini sp. n., broadly ellipsoid to subspherical with outer surface of oocyst wall mammillated (14.0 × 11.9), from 2 SSTs;Eimeria mitraria(Laveran&Mesnil), asymmetrically ellipsoid, bearing 1 or 2 conical projections at the polar end and 2 or 3 at the antipolar end (10.0 × 7.6), from 7 WPTs, 1 MT, 3 FMTs, and 4 IMTs; Eimeria pseudogeographica sp. n., narrowly ellipsoid to slightly ovoid (19.5 × 13.5), from 5 WPTs and 3 FMTs; Eimeria tetradacrutata sp. n., spherical to subspherical with outer surface of oocyst wall mammillated (19.5 × 19.2), from 1 WPT; anEimeriasp. narrowly ellipsoid, bearing 2 conical projections at the polar end and 2 at the antipolar end (23.8 × 13.2), from 1 MT; and Mantonella hammondi sp. n., conical to narrowly ellipsoid, bearing 1 conical projection at the polar end and 2 or 3 at the antipolar end (14.3 × 7.1), from 1 IMT. The overall infection rate for the 63 turtles exami