This study compared preverbal children (ages 3-4) with severe language impairments who were difficult to engage (Group 1) with others who were readily engaged (Group 2). The study focused on transitional episodes of engagement and on frequency of clinician and child verbal communications and nonverbal acts within transitional episodes. Eight clinician-child pairs were studied. Group 1 children spent more time maintained at a low level of engagement, while Group 2 children spent more time maintained at a high level of engagement. Group 1 was less likely than Group 2 to move from a "rising episode" (i.e., rising from low to high levels of engagement) to "maintained at a high level of engagement." Within transitional episodes, when Group 2's clinicians produced two more acts than the children, the engagement level fell. When the number of acts produced by the clinician and child matched almost exactly, the engagement level rose. Group 1's clinicians did not modulate the number of their verbal and nonverbal acts as a function of engagement level within rising and falling episodes. (JDD)