**Purpose**: Although prior studies on biofeedback interventions have shown positive treatment outcomes for many children, research comparing different biofeedback types is lacking. This study examines within-treatment response to ultrasound and visual-acoustic biofeedback treatment, as well as generalization to untrained words, for residual errors affecting the American English rhotic /ɹ/. All participants received both treatments. Individual factors related to overall treatment response are also explored. **Method**: Seven children ages 9-16 years with residual rhotic errors participated in 10 treatment visits. Each visit consisted of two conditions: 45 minutes of ultrasound biofeedback and 45 minutes of visual-acoustic biofeedback. The order of biofeedback conditions was randomized within a single-case experimental design. Acquisition of /ɹ/ was evaluated through acoustic measurements (F3-F2 difference) of selected non-biofeedback productions during practice. Generalization of /ɹ/ was evaluated through acoustic measurements and perceptual judgment of pre-treatment/post-treatment probes. **Results**: Randomization tests indicated that one participant demonstrated a significant advantage for visual-acoustic over ultrasound biofeedback based on within-condition acoustic measures. Three participants demonstrated a clinically significant degree of generalization to untreated words on post-treatment probes. Participants’ auditory-perceptual acuity on an /ɹ/-/w/ identification task was identified as a possible correlate of overall treatment response. **Conclusions**: Most participants responded equally to biofeedback conditions, but one participant showed a preferential acquisition response to visual-acoustic over ultrasound biofeedback. Consistent with previous studies, some but not all individuals with rhotic distortions exhibited clinically significant generalization following a course of biofeedback treatment.