SUMMARY.The growth and recession of macrophytes on a shaded section of the R. Lambourn were documented by a mapping procedure. With the exception ofRanunculusspp., the changes in total cover did not indicate directly the pattern of growth and recession of the macrophyles. Analysis of gross changes, expressed as gains and losses on cover, indicated that colonization of gravel and silt by the dominant macrophyte,Berula erecta, did not vary seasonally. Colonization was at a constant rate of about 8% of the site each month throughout the year and this accounted for 50% of the total number of gains byBerula.Gains ofBerulafromRanunculusshowed an annual cycle with a maximum during the summer whenRanunculuswas in recession. Gains ofBerulafromCallitrichespp. also varied annually but the maximum was during the autumn. Total losses ofBerulawere at a constant rate throughout the year but were to gravel and silt during the winter, toRanunculusin spring and early summer and toCallitrichein late summer and autumn. Analysis of loss ofBerulawith time indicated that the position of theBerulacarpet was constantly changing. The growth and recession ofBerulacould not be linked in a meaningful way to environmental variables.CallitricheandRanunculusboth showed an annual pattern of growth and recession. There was temporal separation of the two macrophytes withRanunculusgrowing mainly in spring and early summer andCallitricheshowing maximum growth in late summer and autumn, and some evidence of spatial separation. The observed differences between years in the growth ofCallitrichecould not be attributed to any of the environmental variables measured.Discharge was thought to be an important variable controlling the growth ofRanunculussince increase ofRanunculusin the spring was positively correlated with the mean discharge at that time. In years when discharge was low, the growth ofRununculusappeared to be restricted by shading from epiphytic algae which accumulated on the plant surfaces under these conditions.