Dealing with violent cancer patients can be particularly challenging. The purpose of this study was to collect data on the frequency, quality, and underlying variables affecting violent behavior as well as to examine the role played by this behavior in the premature interruption of treatment. A total of 388 cancer inpatients were examined by liaison psychiatrists. The data were assessed using the Staff Observation Aggression Scale (SOAS-R) and Psycho-Oncological Basic Documentation (PO-BADO); the quality of psychiatric disturbances was measured with a three-level rating according to "Diagnostic and Statistical Manual of Mental Disorders" (4th ed.) criteria. Nineteen of 388 patients (4.9%) displayed violent behavior. The variable "cognitive limitations" was clearly associated with aggressive behavior. The interaction factor "constantly bedfast, nonterminal phase, and strong feelings of helplessness or subjection," was associated with aggressive behavior as a trend statistically. Eight of 19 inpatients showing aggressive behavior were prematurely released from the treatment facility. In a multivariate model the association of the variable "aggressive behavior" to premature interruption of treatment with unfinished diagnosis and therapy was weighted rather strong. Despite their methodological limitations, these results suggest that members of oncological teams should be able to identify violent behavior and its precursors at an early stage as important factors, which may decrease patient cooperation. (Contains 5 tables and 1 figure.)