The purpose of this study was to examine how readers build orthographic knowledge for irregular words, defined as words that do not conform to conventional phonics rules and patterns. This study tests my theory that readers use phonological decoding, crosschecking and mental markings to read and spell unfamiliar irregular words. Forty-three students in first and second grades participated in the study. One experimental group received instruction in decoding and crosschecking while reading stories containing target irregular words. One control group did not receive any instruction while reading the same stories. A second control group received only vocabulary instruction in target word meanings. Print was not used. Pretests and posttests in target word recognition and vocabulary knowledge were compared. Data indicated there were no statistically significant differences in pretest and posttest scores measuring word recognition of target words and vocabulary knowledge of target words. There were, however, statistically significant differences among pretest scores in word recognition, but not vocabulary knowledge, suggesting students in the vocabulary control group had stronger prior knowledge of the target words. Scores on a spelling posttest were compared across groups. There were no statistically significant differences in scores. Despite the lack of statistically significant differences in scores, this study yields telling evidence about how readers build orthographic knowledge for irregular words. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]