The provision of ventilation air for high-rise multifamily housing has plagued retrofit practitioners and researchers alike. We have been studying the air flows and ventilation systems in high-rise buildings in Massachusetts and in California, and have seen all the horror stories of poorly functioning systems that are neither efficient nor deliver satisfactory ventilation. Frequent problems include the imbalance of supply and exhaust air, the lack of an unobstructed path for supply air, differences in ventilation rates between upper and lower floors and a change in air flow due to seasonal variations in temperature and wind. Based on our diagnostic tests of air flow and air leakage, which we use with our multi-zone airflow computer simulations, we have characterized some common problems and suggest strategies to improve the performance of these systems.