Eight cases of hydatid disease of the abdomen and thorax were diagnosed by fine-needle aspiration (FNA) cytology under ultrasound guidance. The age of the patients ranged from 28 to 60 yr with a median of 34.5 yr; the male to female ratio was 2:6. None of the cases were diagnosed clinically as hydatid diseases but following ultrasonography suspicion of hydatid cyst was raised in two cases. The locations of cysts were the liver in six cases, the lung in one case, and the mediastinum in one case. FNA yielded clear fluid in five cases and turbid fluid in three cases. Laminated cyst wall, scolices, and hooklets were observed in one case, scolices and hooklets were present in two cases, and laminated cyst wall along with hooklets were seen in two cases. The remaining three cases showed only laminated cyst walls which yielded positive reaction with periodic acid-Schiff reaction. Inflammatory cell reaction in the form of neutrophils was observed in four cases, including the three cases where turbid fluid was aspirated. Epithelioid cell reaction was present in one case. None of our eight cases showed any untoward allergic reaction following FNA.