https://communities.sas.com/t5/Statistical-Procedures/maximum-number-of-levels-in-proc-mixed/m-p/54556#M2530 Hi modeler,<BR /> <BR /> Yes, you can have four levels of nested effects. I don't think there is a maximum though keep in mind that PROC MIXED uses iterative estimation algorithm and large number of levels may substantially increase the computation time. Thu, 16 Jul 2009 15:19:49 GMT statsplank 2009-07-16T15:19:49Z https://communities.sas.com/t5/Statistical-Procedures/maximum-number-of-levels-in-proc-mixed/m-p/54555#M2529 Hi all,<BR /> How many levels can you incorporate into a multilevel model in SAS proc mixed? Can you have four, e.g. measurements over time nested within patients nested within providers nested within clinics?<BR /> Thanks for your help. Wed, 15 Jul 2009 05:55:42 GMT https://communities.sas.com/t5/Statistical-Procedures/maximum-number-of-levels-in-proc-mixed/m-p/54555#M2529 deleted_user 2009-07-15T05:55:42Z https://communities.sas.com/t5/Statistical-Procedures/maximum-number-of-levels-in-proc-mixed/m-p/54556#M2530 Hi modeler,<BR /> <BR /> Yes, you can have four levels of nested effects. I don't think there is a maximum though keep in mind that PROC MIXED uses iterative estimation algorithm and large number of levels may substantially increase the computation time. Thu, 16 Jul 2009 15:19:49 GMT https://communities.sas.com/t5/Statistical-Procedures/maximum-number-of-levels-in-proc-mixed/m-p/54556#M2530 statsplank 2009-07-16T15:19:49Z