The controversy over a biological basis for developmental dyslexia is reviewed and illustrated by two case studies of junior high school students who fit the exclusionary criteria for dyslexia but show marked differences in academic abilities. Both students show a severe deficit in sounding out new words (phonological decoding) that has not improved with remediation, despite evidence of average abilities in other cognitive skills. The phonological deficit is consistent with locations of neurological abnormalities found in the brains of dyslexic individuals. Recent findings of abnormal cells and atypical patterns of later‐alization in dyslexia are reviewed. Seven signs are proposed to be characteristic of reading disability that may qualify as dyslexia.