Abstract : Background: Immune thrombocytopenia (ITP) is an autoimmune disorder characterized by heterogeneous bleeding manifestations as well as marked-inter individual variation in response to glucocorticoid (GCs); the 1st line ITP treatment. This may be due to Pgp as steroids outside the intracellular space thus decreasing its intracellular concentration. Methods: The study investigated the relation between single nucleotide protein; the product of ATP binding cassette B1( ABCB1) gene. It is involved in effluxing drugs polymorphism (SNPs) in ABCB1gene and the variable response to oral prednisolone treatment in 100 Egyptian ITP patients. Clinical response was measured during 1st 28 days and compared with C3435T and G2677T SNPs determined by PCR REPLF technique. Results: No significant difference in C3435T between ITP patients and control. Carriers of mutant allele of G2677T were significantly higher in ITP patients compared with the control group (p value :02) suggesting possible role in disease predisposition. Conclusion: There was no significant relation between these two SNPs and age of onset of the disease , initial platelet count, response to steroid therapy .