I investigated reproductive output in 24 adult female pond sliders (Trachemys scripta) collected in early and mid-May 1997–1999 from central Arkansas. All females were gravid or possessed follicles of ovulatory size, although one had deposited an earlier clutch. Dissected females each also had 2–3 sets of enlarged follicles, suggesting an annual clutch frequency of 3–4 (positively related to body size). Clutch size averaged 10.7 eggs and tended to increase with female size. Egg size averaged 36.7 × 22.3 mm and 10.73 g, was not related to female size or clutch size, and was remarkably constant across the species' range, suggesting selection for optimal egg size. Relative clutch mass (RCM: clutch mass/gravid body mass) averaged 7.9% and decreased with increasing female body size. Comparisons across other populations of sliders revealed distinctly different reproductive strategies for T. s. elegans and T. s. scripta. Despite their heavier bodies (deeper shells), T. s. scripta produces relatively fewer (8.3 vs. 12.3) similar-sized eggs, resulting in much lower output per clutch (RCM: 3.8% vs. 8.6%). This exaggerated reproductive output no doubt contributes to the success of T. s. elegans as a globally invasive taxon. Clutch size increased with body size for both subspecies across populations, but both parameters increased with latitude only for T. s. elegans. In contrast, egg size increased with body size only in T. s. scripta and did not vary with latitude in either subspecies. These data are consistent with optimal egg size theory in that increases in reproductive output are accomplished primarily by increases in clutch size rather than egg size.