In the intervals between psychotherapy sessions, patients often make use of the experiences that they have during sessions with their therapists, but these "intersession processes" (ISP) have been largely neglected in psychotherapy research. This study presents a German version of the Intersession Experience Questionnaire (IEQ, Orlinsky et al. ) called the Inter-Session-Fragebogen (ISF). The ISF was used to study a total of 3.778 intersession intervals in 249 therapy episodes involving 229 patients. The factor structure of the ISF appears to be stable over therapy (up to 25 or even 50 sessions), and also over therapy settings (outpatient, day clinic, inpatient). Just as in the original American samples, there were evidently cross-culturally invariant factors like "Recreating the therapeutic situation", "Applying therapy," and "Relationship fantasies". The emotional qualities of ISP are assessed by two independent factors, called "Remoralizing emotions" and "Negative emotions" (regarding therapy). Differences between therapy settings are evident concerning intensity and trajectories of the factor scores over time.