Abstract: The occurrence of aflatoxins B1, B2, G1 and G2 in commercial dog food was investigated. Fourteen dog food cereals-based from dog shops were collected. The extracts were cleaned- up through commercially immunoffinity columns followed by fluorescence detection and pH analyzed. Dry and semi-dry adult food showed pH between 6.0-6.2 in average aflatoxins 24 and 17.5 �g kg 1, respectively. The dry and semi-dry puppy food with pH (6.2- 6.8) and levels ranged from 17-29 �g kg 1; three semi-dry adult food with a pH>6. The 42.85% of total foods were above the maximum limit established in Mexico. These results show the occurrence of aflatoxins, indeed the regulatory aspects still need harmonized; also the importance of pH in the performance of immunoaffinity column.