The aim of this paper is to study the effect of Laser radiation on clinical parameters of human blood. Interaction of laser radiation with biological tissue has wide applications in clinical pathology starting from diagnosis of the disease to the treatment. Choice of blood is taken as an object for investigating the effect of laser radiation on clinical parameters since blood is a connective component of all biological objects. The study is an attempt to investigate the in vitro effects of lowlevel laser radiation (LLLR) on hematological parameters of the human blood, such as complete blood count (RBC, WBC, and Platelet count), Hb concentration, Hematocrit value (HCT), Mean Cell Volume (MCV) and Mean Cell Hemoglobin Concentration (MCHC). Present investigation mainly concerned with the alterations caused by LLLR action on blood cells of fresh blood samples obtained from healthy adult people.