Immobilized algal beads were utilized to monitor nutrients and metals in several streams around Hong Kong. Cells of Chlorella vulgaris, a single celled microalga approximately 3 - 6 µm in diameter, were immobilized in alginate beads with a density of approximately 1 x 106 cells bead-1. The algal beads were deployed for five days in a variety of Hong Kong streams ranging from pristine hillside streams to a rural stream heavily polluted with piggery wastewater. Algal growth was monitored through changes in chlorophyll a and cell number. The changes in chlorophyll a bead-1 was found to be a more suitable parameter to indicate nutrient status of streams than cells bead-1. Increases in chlorophyll a bead-1 ranged from 72 % in pristine streams (ortho P concentration < 0.01 mg 1-1) to 876 % in a nutrient enriched stream (mean ortho P concentrations of 0.48 mg 1-1). Significant positive correlations were found between the log values of percentages increase in chlorophyll a bead-1 and log ortho P concentrations in stream water (r = 0.811, P < 0.01). Moreover, log values of percentages increase in chlorophyll a bead-1 were inversely proportional to log inorganic N:ortho P atomic ratios of stream water (r = - 0.814, P < 0.05). Increases in algal cells bead-1 ranged from no change to 478 % but were not correlated with any nutrient concentration. In terms of metal monitoring, algal beads adsorbed metals during stream exposures and Al, Cu, Ni and Zn were all adsorbed and concentrated by algal beads. The metals adsorbed onto the algal beads were desorbed and recovered by placing the exposed beads in 0.1 M HCl solution, where the low pH caused the bound metals to be released from the beads into the HCl solution. The recovered metals were more concentrated in the HCl compared to their concentrations in stream water, which allowed easy analysis. The concentration factors of the algal beads, in all the streams, were Al 1268 - 31327, Cu 924 - 25224, Ni 733 - 808, and Zn 9866 - 29570, and these values were comparable to those reported in the literature employing similar biomonitors, such as macroalgae. High concentrations of Cu and Ni were adsorbed by algal beads exposed in one stream, Tai Wai Nullah, with the values of 926 µg Cu g-1 dry wt. algal bead and 120 µg Ni g-1 dry wt. algal bead. In this particular stream the concentrations of dissolved Cu and Ni in stream water were 102 µg 1-1 and 149 µg 1-1, respectively. The metal adsorbed did not seem to have any toxic effects on the immobilized algal cells, nor did immobilized cells affect metal adsorption by beads. However the alginate matrix deteriorated to varied extents in streams, ranging from minor changes to complete dissolution of the alginate beads. Ortho P appeared responsible for the degradation of alginate matrix and shrinkage of beads started to appear when ortho P concentration exceeded 0.5 mg 1-1. A significant negative correlation was found between bead deterioration (indicated by reduction in dry weight of algal beads after five days stream exposures) and ortho P concentrations (r = - 0.711, P < 0.05). This study demonstrates that alginate immobilized algal beads could be used to indicate nutrient status of streams in Hong Kong through monitoring changes in chlorophyll a bead-1 over five days exposure. At the same time, metals adsorbed onto the alginate beads provided a good indication on degree of metal contamination in stream water.