This study explored the relations between reading comprehension and two memory capacities, short-term memory (STM) and working memory (WM), for adults who read between the third and eighth grade levels. With a sample of 407 adults from two countries, we computed correlations among measures and conducted hierarchical regression and commonality analyses for reading comprehension. Reading comprehension had moderate positive correlations with STM and WM. Additionally, STM and WM jointly accounted for approximately 19% of the reading comprehension variance and uniquely contributed approximately 4% and 7% of the variance, respectively. The predictive utility of memory to reading comprehension was greatly reduced after controlling for age, word reading, fluency and oral vocabulary. WM appears to be a slightly stronger predictor of reading comprehension than STM for struggling adult readers. However, the overall contributions of memory capacities to reading comprehension are much smaller than those of reading-related skills. [For the corresponding grantee submission, see ED587171.]