In 4 experiments, preschoolers and kindergarteners were asked to pronounce the initial consonants of spoken words. Children performed better on short words, such as bay, than on long words, such as bonus. Words with initial consonant clusters, such as brow, were more difficult for the children than words without initial consonant clusters, such as bar. A consonant cluster at the end of the word did not harm performance. Children did relatively well on words like suppose, for which the word's first syllable, /»/, constitutes a correct answer on the initial consonant isolation task. Children did more poorly on words like satin, for which this was not the case. Thus, the linguistic structure of a word affects children's ability to isolate the initial consonant. Implications for the design of phonemic awareness instruction are discussed. Children's ability to analyze spoken words into phonemes has received a good deal of attention from researchers and educators in recent years (see Adams, 1990; Brady & Shankweiler, 1991; Goswami & Bryant, 1990; Gough, Ehri, & Treiman, 1992; Rieben & Perfetti, 1991; Sawyer & Fox, 1991). The research reviewed in these volumes shows that phonemic awareness plays an important role in learning to read and write an alphabetic system. The research further shows that children who lack phonemic awareness skills are at risk for developing reading problems. On a more positive note, phonemic awareness can be taught. Such teaching improves children's reading and spelling performance. To design effective phonemic awareness instruction, detailed information about specific phonemic awareness tasks is needed. How do children perform these tasks? Do they do better with some kinds of words than others? Answers to these questions can help in the design of phonemic awareness instruction. For example, if some types of words are easier to analyze than others, the easy words can be taught first. Harder words can be introduced only after children have mastered the easier ones. The long-term goal of the research reported in this article is to improve phonemic awareness instruction, and ultimately reading, through the study of linguistic factors that affect children's performance in phonemic awareness tasks. Researchers and teachers have used a variety of phonemic awareness tasks. These include counting phonemes (How many sounds do you hear in fishT), deleting phonemes (Say fry without the/), comparing phonemes (Does dog end with