Two experiments were carried out at three areas of Cairo City; El‌Helmia EI-Gadida, EI-Saieda Zeinab and Abbasia to study the effect of certain additives (powder milk, fish meal, blood meal and bone meal) on: 1. The palatability of crushed maize bait. 2. The efficiency of zinc phosphide crushed maize bait. Data obtained from the first experiment revealed that all tested additives led to an increase in the consumption of crushed maize. The consumption could be arranged in the following decreasing order 100 % for maize + powdered milk > 23.02% for maize + fish meal > 6.00 % for maize + blood meal > 4.00 % for maize + bone meal > 1.06% for maize alone. These results ured to carry out the second experiment to investi‌gate the effect of the tested additives on the efficiency of 1% Zinc phosphide bait loaded on cruhed maize. Before and post-treatment pop‌ulation density was determined by three methods: 1. The active burrow holes (Abdel-Gawad and Maher AN, 1982). 2. The food tracks activity method (El-Sherbiny and Awad, 1987) 3. The gnawing activity method (EI-Sherbiny et at, 1987). 1% zinc phosphide + 2% of each of the tested additives was used. Results showed that, within the three above mentioned methods, all tested additives led to a higher significant reduction in rodent popula‌tion than that of the control. Increasing the population reduction due to different additives followed the same trend achieved in case of the ef‌fect on increasing the consumption, i.e. powder milk> fishmeal> blood-meal>control. So, the higher the consumption the more successful the control is.