Orangethroat darters Etheostoma spectabile occupying thermally contrasting streams within the same watershed were tested for differences in thermal responses by comparing their critical thermal maxima (CTM) and short-term growth. Individuals from a spring branch population had a lower CTM, better growth at low temperatures and more inhibited growth at higher temperatures compared to individuals collected from a thermally variable adjoining stream reach. The findings support the contention that intraspecific differences in thermal tolerance and growth may exist at relatively localized scales within a small watershed.