Several methods have been presented by Adams (1959) to determine adsorption kinetics of bacteriophages. One way to measure the adsorption efficiency of cyanophages is to assay for free unadsorbed phages (Suttle and Chan 1993). The principle of this assay is to add a known quantity of viruses to host cells (e.g., at an MOI = 0.01 to 0.1). Over a period of 1 to 2 h, small subsamples of the virus:host solution are removed ca. every 15 min and diluted 100-fold to stop further adsorption. The host is then separated from free viruses by centrifugation, and the number of free viruses remaining in the supernatant determined by plaque or end-point dilution assays. A plot of the abundance of free viruses remaining in solution as a function of time should produce a straight line. The slope of this line is then used to calculate the adsorption rate.This procedure can be adapted for other host\u2013virus systems. The example given is for host BBC1 and cyanophage BBC1-P1 (Suttle and Chan 1993).