This 300-plus page set of typed notes from the 1972 NATO summer school on The Theory and Pactice of Systems Modeling and Identification discusses recursive estimation from a nontheoretical engineering view. The CAPTAIN computer package for time-series analysis is introduced by the author and presumably used to prepare the IV-AML estimates presented in the text. Statisticians and mathematicians will find little new in this presentation, but anyone wishing an introduction to time series analysis and recursive parameter estimation of the 1960s should find Young’s presentation worth examining. The several practical examples used in the text are both meaningful and interesting.