Pseudobasophilia is an analyzer phenomenon whereby abnormal cells in the peripheral blood are counted as basophils. Previously described on the Technicon H-series hematology analyzers, pseudobasophilia is also a technical consideration on the Advia 120. Sometimes seen as a hindrance to inexperienced users, an understanding of the basophil (baso) method and baso cytogram produced by the Advia 120 can be utilized to alert the laboratory scientist and clinician to the possible presence of an abnormal cell population in the peripheral blood. Cytogram analysis should form part of routine laboratory practice and the present annotation aims to offer some assistance to users of the Advia 120 and Advia 2120.