This article documents the number of target persons participating in the panel surveys of the National Educational Panel Study (NEPS) as well as the number of respondents who temporarily dropout and of those leaving the panel (attrition). NEPS comprises panel surveys with six mutually exclusive starting cohorts covering the complete life span. Sample sizes, numbers of participants and temporary as well as ﬁnal dropouts and participation rates are reported in detail for each wave and for subsamples, if applicable. Sample particularities, such as the conversion of temporary dropouts into ﬁnal ones, are elaborated on. All ﬁgures presented are derived from the corresponding Scientiﬁc Use Files (SUFs) published by February 1, 2018. Selectivity due to attrition (i.e., ﬁnal dropouts) is studied. For this purpose, we examine how attrition distorts the NEPS samples with respect to relevant design variables (such as stratiﬁcation criteria) and panel member characteristics (like sex and birth year). In detail, we study the panel status of each panel member, that is being part of the panel or having dropped out ﬁnally, along all of the panel waves with respect to starting cohort and population speciﬁc characteristics. We conclude this article with some recommendations for dealing with the detected selection bias in statistical analyses.