The incidental discovery of neutropenia during routine blood counting represents a common problem for clinicians. However, there are no reported data of systematic evaluations of adults with incidental neutropenia. As such, this was the aim of the present study. Ninety-seven adults with incidental neutropenia were submitted to a clinical and laboratory approach including medical evaluation, complete blood count (CBC), serial CBC, direct and indirect antiglobulin test, bone marrow smear and biopsy, assessment of folate, vitamin B12 and iron status, serum liver enzymes, serum proteins, serological exams for hepatitis B and C virus, cytomegalovirus, mononucleosis, human immunodeficiency virus and toxoplasmosis, detection of lupus erythematosus cells, antinuclear and anti-DNA antibodies and rheumatoid factor, dosage of free thyroxin and thyrotropin, chest roentgenogram and abdominal echography. Chronic idiopathic neutropenia of adults was identified in 34.0% of the individuals, neutropenia due to exposure to chemical agents was seen in 16.5%, infectious diseases in 9.3%, autoimmune diseases in 9.3%, haematological diseases in 9.3%, thyroid disorders in 8.2%, ethnic neutropenia in 7.2%, drug-related neutropenia in 2.1%, cyclic neutropenia in 2.1% and iron deficiency in 2.1%. Recovery or improvement of the neutrophil count was seen upon treatment or recuperation from infectious, autoimmune, haematological and thyroid diseases and iron supplementation. We conclude that the evaluation of individuals with incidental neutropenia using a structured approach may make the identification of clinically silent diseases possible, and provide an opportunity for early treatment, avoiding complications of the diseases and consequences of neutropenia.