This study examined phoneme acquisition in three phonologically impaired children to determine whether treatment needed to be provided continually until correct productions were consistently observed during conversation. This was done by examining the effects of withdrawing treatment on several target phonemes at predetermined performance levels. In addition, production of the target behaviors in untrained single words versus connected speech was compared as measures for monitoring progress during the phoneme acquisition process. Both ABA(B) and multiple baseline time series designs were employed. The results indicated two general patterns of phoneme acquisition. In one, the children continued to progress in phoneme acquisition, even though direct treatment on the target behavior had been withdrawn relatively early in the acquisition process. In the other, the children failed to continue their progress in phoneme acquisition when treatment was withdrawn, requiring the reintroduction of treatment until high levels of correct production were maintained over several weeks. In all cases, production of the target behavior in untrained single words and connected speech reflected a similar phoneme acquisition trend.