The combination of a rising population and increased food demand has placed tremendous pressure on the land resources of Bangladesh. These pressures are exacerbated by the annual wet-season ¯oods which frequently devastate much of the agricultural land. Successive governments have therefore sought international aid to assist in the development of ¯ood control measures. Of particular importance are 14 major schemes which aim to provide protection from 20±25 year return ¯oods by the construction of earth-embanked enclosures. There is no doubt that these schemes have been very successful in protecting valuable agricultural areas from ¯oods and hence increasing agricultural production. There is, however, growing evidence from a range of sources for long-term deterioration in soil fertility within the project areas. The study reported here is the ®rst to systematically examine the changes taking place in soil properties following the establishment of a ¯ood control, drainage and irrigation project. Comparison of two soil series, sampled from within and without the project area, demonstrate that within six years of project establishment, signi®cant adverse changes have occurred in several soil properties; these include increasing acidity and a decline in available nutrients. The changes are attributable to a combination of poor management strategies and the absence of the annual ¯ood input of silt. As Bangladesh cannot aord any decline in agricultural output, it is vital to establish whether adverse changes recorded here are occurring in other projects. This can be achieved by the establishment of a nationwide programme of soil fertility monitoring.