This article describes the influences of phonemic factors on pitch frequency patterns in Japanese words for the purpose of improving synthetic speech quality. To clarify the influences of consonants in the initial position upon pitch patterns, pitch frequencies of onomatopoeic words and Japanese words with long syllables in the initial position are analyzed. The phenomena of contradiction and compensation between the accent-related tone and the consonantal pitch height are observed. It is shown that phonological accent patterns can not always be distinguished in pitch frequency patterns in words containing a long syllable in the initial position, and that the phoneme-related effects should be taken into account to produce pitch frequency patterns. Finally, the contribution of these observations for improving the naturalness of synthesized speech is discussed.