A survey on the geographical distribution of Chnootriba similis (Thunberg), formerly known as Epilachna similis, was undertaken from 2001 to 2003 in the main cereal-growing areas of Ethiopia. The population density of the insect was estimated by sweep netting (100 sweeps/farm). In addition, more detailed studies on seasonal and annual fluctuations in population density of C. similis were carried out in southern Ethiopia between 2002 and 2003 by sampling 10 quadrants of 0.25 m2 per farmer's field. The damage levels were determined using scores of 0–9. The survey revealed that C. similis is widely distributed in different parts of the cereal-growing regions of Ethiopia. It was observed that the beetles had spread to altitudes ranging from 1217 to around 3000 m asl. However, the variations in population densities of C. similis cannot be directly attributed to altitude, as highly differing population densities in similar altitudes of different locations were recorded. Annual and seasonal variations in population density were observed in different areas of the southern part of Ethiopia. These results suggest that C. similis has a sporadic nature and can occasionally build up to outbreak levels. Beetles fed on both cereals (barley, wheat, tef, maize, sorghum and finger millet) and wild grasses (Leersia hexandra (Sw.), Avena abyssinica (Hoechst) and Lolium temulentum (L.)). Population densities and damage levels on the cereal crops varied considerably with the highest densities and damage levels on barley.