Dear, Are there R packages for Generalized Estimating Equations that provide the possibility to implement a three-level structure? My data consist of repeated measures of subjects (AutoRegressive correlation is expected) within different groups (I expect the behavior of individuals from one group to be correlated), with individuals not balanced over groups. So, I have observations at time t (level 1) nested within individuals (level 2) and individuals nested within groups (level 3). The implementation of a two-level structure is rather straightforward in for instance "geepack". At first, I thought that by providing a user-defined correlation structure in ?geepack?, I could create such a 3-level structure. However, after further investigation (i.e. the single hierarchy id-vector) it seems to me that this is not the way to go. Are there suggestions for how to implement such a three-level structure? Best regards, Bram -- Bram Van Moorter Centre for Conservation Biology (NTNU), Norwegian Institute for Nature Research (NINA) Trondheim (Norway) email: ?Bram.Van.Moorter at gmail.com website: http://ase-research.org/moorter phone: +47 73596060