The papers presented in this special issue highlight three theoretical topics central to the reading comprehension research. The first relates to the component skills of reading comprehension performance. Among the multiple linguistic and cognitive skills involved, vocabulary retained much of the researchers' attention. Three papers described the influence of vocabulary on various aspects of comprehension. The second topic is tied to the assessment of reading comprehension and the analysis of individual differences. Despite the multidimensional nature of the reading comprehension process, most assessment tools provide a single measure of performance. Four papers focused on analyzing the specific dimensions of comprehension being assessed by existing and novel tests. The third topic is relevant to the teaching of comprehension and the prevention of reading comprehension difficulties. A final paper presented the findings of an intervention study designed to enhance oral language in kindergarten.