2 cases of portal, splenic and superior mesenteric vein thromboses related to prolonged stay at high altitude are presented. Both presented initially with innocuous appearing vague pain in abdomen with no physical signs. Later hepatosplenomegaly, and pleural effusion (left) was also detected. Diagnosis was based on CT scan and colour Doppler study showing thrombosed veins and porto-systemic collateral. 1 patient developed a large splenic haematoma requiring splenectomy. Both were managed with early anticoagulation and have done well in the short follow up.