Abstract: Using the method of weighted estimation equation, under the generalized casecohort design scheme, we gave the estimation of regression coefficients in Cox’s model for lengthbiased data. Under appropriate conditions, we proved that the obtained estimators were consistent and asymptotic normality, and the asymptotic variance was explicit expression. It could be estimated by the plugin method in practical application.

Key words: lengthbiased data, generalized casecohort design, Cox proportional risk model, composite estimation equation