Background: Thrombocytopenia is defined as a platelet count of less than 150 9 103 ll. It is commonly diagnosedand has attracted more interest from the researchers inpregnant women during the last 20 years, especially inhypertensive pregnant women. Aim To assess the incidence of thrombocytopenia in hypertensive pregnant women during the third trimester ofpregnancy. Methods :Five hundred forty–four pregnant women were included in this study from a total of 10,272 admitted at the Obstetrics and Gynecology Department at Tripoli Medical Center during January–August 2007. Frequent blood pressure monitorings and full blood counts were performed in several medical follow ups. They were not known to be HBV, HCV, or HIV positive women before pregnancy, and none was reported to have evidence of HBV, HCV, or HIV upon performing HBs–Ag, anti–HCV antibody, orHIV–antigen positive tests. Data were arranged in Excel Microsoft program version 2010, and statistically analyzed by SPSS windows program version 17. Results Five hundred and forty–four women were hypertensive according to WHO hypertension definition criteria. Sixty–seven women had only one reading of high blood pressure, while 39 women fulfilled HELP syndrome criteria (hemolysis elevated liver enzymes low platelet). These 39 women were excluded from the study. Therefore, only 438 pregnant women remained eligible for the study. The mean age was (32.56 ± 1.5), with their ages ranging between 18 and 49 years. Most of the included women were primi–gravida 179 (39 %), gravid 2, para one were 72 (16.4 %), and the rest were gravid 3 or more (42.6 %). The blood pressure was 140–160/90–110 mmHg in 365 women (83.4 %), and 73 women (16.7 %) had blood pressure readings more than 160/110 mmHg. Mean platelets count was (206.49 9103/ll ± 3.35), and ranged between (41.0 – 449.0 9103/ll). Thrombocytopenia (less than 150 9 103/ll) was recorded in 103 women (23.5 %). All pregnancy cases were delivered safely with no fetal complications. Conclusion :Gestational thrombocytopenia (GT) is recognized as a major cause of thrombocytopenia particularly in hypertensive pregnant women during the third trimester. Careful follow up during and after pregnancy for those women is recommended.