The stochastic approximation procedure with series of delayed observations is investigated. The procedure is formed by modifying the Robbins–Monro stochastic approximation procedure to be applicable
in the presence of series of delayed observations. The modified procedure depends on a new base concerning the relation between service time of the series and service times of its components. Two loss
systems are introduced for application to the proposed procedure. This new situation can be applied to
increase the production of items in many fields such as biological, medical, life time experiments, and
some industrial projects, where items are realized after random time delays. The efficiency of the procedure is computed. Our proposal is general and we expect that it can be applied to any other stochastic
approximation procedure