This case presentation describes a 29 year-old female who developed a severe ovarian hyperstimulation syndrome (OHSS) with ascites and a right-sided pleural effusion following in-vitro-fertilisation. A total of 4,2 l of pleural fluid was removed during 3 thoracocenteses. The symptoms as well as the fluid production ceased after 2 weeks. The OHSS is altogether a rare, but potentially life-threatening complication of in-vitro-fertilisation. Due to the well-characterized clinical setting in which the syndrome appears, there are only few differential diagnoses to consider. OHSS is likely to originate from altered capillary permeability, but its pathogenesis is not yet fully understood. Clinical symptoms usually resolve within 2 weeks of supportive therapy. In case of persistency, however, especially pulmonary embolism and infectious causes of pleural fluid production have to be excluded.