Recent studies have attempted to evaluate the use of acoustic analysis in the assessment and treatment of phonological disorders [K. M. McGregor and R. G. Schwartz, J. Speech Hear. Res. 35, 596--603 (1992); Tyler et al., J. Speech Hear. Res. 36, 746--759 (1993)]. This investigation follows a child during therapy for multiple speech sound errors. Two speech sounds, a fricative /f/ and a stop consonant /t/, were chosen to represent two distinct consonant types in error which were being targeted in therapy for the period of this investigation (3 1/2 months, with a 1-year, 3-month followup). The child's productions of these sounds were probed during a picture-naming activity which included the target sounds in both prevocalic and postvocalic positions. On-line clinical judgments (correct, incorrect, absent) were made during audiotaping of the child's productions. Audiotape recordings were then analyzed spectrographically using a Kay Elemetrics CSL model 4300. Both temporal and spectral dimensions were documented to track changing sound productions across time and were compared to the perceptual judgments. Measurable acoustic features predicted perceptual sound changes to a limited degree. Results are compared to prior studies. Implications for the inclusion of acoustic analysis in the assessment and intervention of phonological disorders are discussed.