Background: Transient stress lymphocytosis is an under recognized acute self limiting entity characterized by absolute lymphocyte count ALC > 4x109/Lt , frequently seen in cardiac and obstetrical emergencies, nonsurgical traumas, epilepsy etc. this study aims to analyzed the clinic-pathological features of the patients of TSL in a tertiary care Cardiology institute in North India. Methods and Results: A total 142 cases were evaluated with a follow up of 15 days detail clinical history, examination finding, biochemical and hematological investigations and where ever possible the immunophenotypic data were analyzed and in 122 cases ALC returned to normal level followed by proportionate increase in neutrophil and platelet count. On immunophenotyping there was increase in all subset of lymphocyte including T cell, B cell and NK cell. Conclusion: Contrary to the expected neutrophilic response, a few acute stress full conditions are known to be associated with absolute lymphocytosis that is transient type and most often ignored by the treating clinician as many time in subsequent investigations the ALC was found to be normal. Usually this condition is associated with poor outcome.