This study examined interrater reliability and sensitivity to change of the Achievement of Therapeutic Objectives Scale (ATOS; McCullough, Larsen, et al., 2003) in short-term dynamic psychotherapy (STDP) and cognitive therapy (CT). The ATOS is a process scale originally developed to assess patients' achievements of treatment objectives in STDP, but further operational definitions have led to a theoretically neutral assessment device, making it applicable to other treatment modalities as well. Videotapes from a randomized controlled trial comparing the effectiveness of STDP and CT for patients with Cluster C personality disorders were rated by independent raters, typically at Sessions 6 and 36. The results indicated good to excellent interrater reliability, as well as adequate sensitivity to change in theoretically expected ways, in both STDP and CT. The results lend further support to the psychometric soundness of the ATOS and show promise for its use when comparing STDP and CT. (Contains 1 footnote and 2 tables.)