INTRODUCTIONMany concrete structures such as those with seismic provisions@ post-tensioning@ and high-strength concrete are difficult to consolidate because of congested areas within the formwork. This congestion can result in structural inadequacy and time-consuming and expensive remedial work. Various techniques have been employed to alleviate this type of problem. This document presents an overview of the factors contributing to the problem@ the consequences of inappropriate concrete procedures in these areas@ and recommended practices to minimize the problem. As a prerequisite to successful concreting in congested areas or difficult placing conditions@ it is important that architects/engineers become more aware of how their designs will be constructed@ and that constructors become more aware of special procedures and necessary precautions. Most importantly@ communication between the architect/engineer and constructor is essential to insure that the design details@ construction materials@ and procedures are compatible.