There is a need for basic readability research and for an easily applied and accurate new readability formula. Two steps taken toward the development of such a formula are the revision of a vocabulary list for primary grades and the combination of reading exercises given at different grade levels into a single scale of ascending difficulty. Much recent readability research seems to rework old topics while ignoring current areas of needed research. In 1852, Herbert Spencer anticipated readability discussions in an article that emphasized economizing the reader's attention, anticipated syntactic and semantic readability features, and suggested four variables now considered in devising readability formulas: syllable length, word familiarity, word abstractness, and sentence length. Recent developments have facilitated the use of these variables in readability. Future research should be devoted to the relationship of readability to cognitive and affective variables, orthographics, graphics design, and developmental reading. The development of vocabulary skills should be considered in conjunction with the development of skills involving decoding, syntactic patterns, and inferencing; and lists should be developed that show the developmental sequence of these skills in major reading series. Research has been conducted that can serve as the basis for such work. (GW)