[show abstract][hide abstract] ABSTRACT: Appropriately timed extraction of a carious first permanent molar can result in favourable mesial drift of the second permanent molar when space is not required for orthodontic treatment. However, when the second deciduous molar adjacent to the extracted tooth is not removed, distal drift of the unerupted second premolar may occur. This paper discusses three patients who had first permanent molars extracted without removal of the adjacent second deciduous molar, encouraging unfavourable distal drift of the second premolar in the first two cases. Timely extraction of the second deciduous molar in the third case should prevent this orthodontic problem. CLINICAL RELEVANCE: Treatment of gross caries in a first permanent molar requires assessment of the patient's orthodontic status prior to treatment planning.