Side effects, adverse treatment reactions, and negative outcomes are relatively neglected topics in the vast clinical literature on psychoanalytic therapies. This article discusses numerous contributory elements and zooms in on the contribution of therapist factors. We present definitions, briefly summarize the state of outcome research, and specifically mention the high attrition rate in psychotherapy and psychoanalysis. Factors shown to contribute to negative effects include incorrect diagnoses, unfavorable external conditions, constitutional factors, and modifications of the ego. We concentrate on examining the role of countertransference and other therapist factors. The article closes with a clinical perspective that raises a question about the analyst's ethical responsibility to inform new patients about the possibility of side effects, damaging consequences, and incomplete or negative outcomes.