Some basic issues in constitutive modeling are examined. The first concerns the requirement of material frame indifference, the commonly used version is analyzed under the restriction that the effect of relativity is negligible. The second deals with the entropy production inequality in the modeling of large scale motions and the uncertainty involved in formulating such an inequality as a constraint in developing constitutive relations is discussed. Finally, the use of Lagrangian frames and reference configurations and related questions concerning the development of a constitutive model for turbulent flows of a fluid, on the basis of laminar flows of that fluid, is discussed. © 2003 Elsevier B.V. All rights reserved.