In one inner London district health authority, the immunisation status of children attending their routine school entry health interview was reviewed over four terms. During the course of these interviews, school nurses completed a questionnaire with parents that asked for their child's immunisation history and details of family and social background. Parental reporting of immunisation history was compared with district health authority records. Only 56% of children reviewed were found to be fully immunised, although a substantial number (386) of the 513 partially immunised children required only a preschool booster. Four percent (54) of the children had received no immunisations; a disproportionately high number of these were recent immigrants. Mechanisms for identifying unimmunised children before they enter communal groups need to be established.