Dissertation (MSc Pediatric and Child Health)Background: Early initiation of comprehensive sickle cell disease (SCD) care with interventions such as hydroxyurea (HU) and transfusion programs have significantly been related to reduced morbidity and mortality among children with SCD. Despite these proved benefits, utilization of hydroxyurea for control of SCD related complications among children with this condition in low-and middle-income countries remains low. Objective: To determine the effect of Hydroxyurea Utilization on incidence of Sickle Cell related complications among children with Sickle cell disease in Dodoma. Method A two-arm retrospective cohort study, 1st arm with no hydroxyurea and 2nd arm with hydroxyurea was conducted at Dodoma Regional Referral Hospital (DRRH) and St. Gemma hospital from November 2018 to March 2019. One hundred and twenty-two (122) children aged 1 to 18 years with SCD attending DRRH and St. Gemma hospital were enrolled (61 on HU and 61 not on HU). A structured questionnaire was used to collect demographic information about the disease profile. The collected information based on Incidence of SCD related complications 6 months prior to this study as well as the treatments received. Blood samples for Full blood count (FBC) and High-Performance Liquid Chromatography (HPLC) were collected for assessing Hb level, neutrophil count a platelet count and HbF % and HbSS %. Routine care and other supportive management according to clinical presentation were given. Data were analyzed using SPSS version 25, Continuous data were summarised in descriptive analysis. Categorical data were reported as proportion or percentage while continuous data were reported in mean (SD) and median (IQR). Categorical data were analyzed using two by two tables to calculate the relative risk. The p-value of < 0.05 was considered statistically significant. Result: A total of 122 children with SCD were enrolled whereby 56.6% were male children with a median age of 5 years IQR (2.63-8.29). Children on hydroxyurea were reported to have less incidence in disease-related complications such as requirement for blood transfusion 8.2%by 0.22 RR, number of admissions 31.1% c RR 0.45, fever 14.8% by RR 0.23, compared to those who were not on HU therapy. Moreover, children on HU had higher fetal hemoglobin levels with median of 15.6 and IQR (12.15 – 21.75) compared to a non-HU group with median of 8.4 and IQR (4.95 – 12.35). like neutropenia and thrombocytopenia among hydroxyurea group compared to no hydroxyurea group, shows relative risk of 1.0 and 1.1 respectively, while skin darkening and nail changes there where no one on the non-hydroxyurea group observed with these complications. Conclusion: The majority of the children on HU show less incidence in SCD related complications presented by hospital admissions, blood transfusions and increased level of HbF in the period of 6 months with remarkable tolerance to drug