In the present study, nanostructured manganese zinc ferrite of 11 nm grain size was synthesized by co-precipitation technique and subsequently suitably heat treated to obtain higher grain sizes. The plot of temperature dependence of dc conductivity shows the semiconducting nature of samples. The observed changes in the electrical conductivity have been attributed with the influence of structural ordering upon annealing. The observed decrease in conductivity when the grain size is increased from 11 to 69 nm upon annealing is clearly due to the structural ordering which is evident from FESEM. (C) 2012 Elsevier B.V. All rights reserved.