The current investigation aim to study the possibility of preparing yoghurt from buffaloe's milk mixed with different levels of potato, sweet potato or various mixtures of them.  Acidity developed in all the treatments.  Increasing the level of added potato or sweet potato or their mixtures resulted in an increase in the content of total volatile fatty acid (T.V.F.A) and total carbonyl (T.C).  However, fat content (F), total nitrogen (T.N.), non-protein nitrogen (N.P.N), soluble nitrogen (S.N) declined with increasing the added amount of potato, sweet potato or their mixtures.  All the treatments have no coliform bacteria or Staphylococcus aureus.  However, molds and yeasts were detected after 10 days of cold storage.  Spore forming bacteria were found in all treatments, as they were not affected by the heat treatments, but the control yoghurt had higher total bacterial, proteolytic and lipolytic counts compared with the potato or sweet potato based yoghurts.  Lower total points of sensory evaluation were given to yoghurt containing the potato or sweet potato as compared with (control) yoghurt.  Amongst the former, yoghurt containing 5% potato or 5% sweet potato or a mixture of (5+5%) gave scores more similar to those of the control.  Yoghurt-mixed with 5% potato, 5% sweet potato or a mixture of them (5+5%) could be recommended.  This leads to decreasing the cost of the final product due to the lower price of potato or sweet potato.