A method for determining a measure of the concentration of analyte molecules or particles in a fluid sample, comprising: exposing a plurality of capture objects that each include a binding surface having affinity for at least one type of analyte molecule or particle, to a solution containing or suspected of containing the at least one type of analyte molecules or particles; immobilizing analyte molecules or particles with respect to the plurality of capture objects such that at least some of the capture objects associate with at least one analyte molecule or particle and a statistically significant fraction of the capture objects do not associate with any analyte molecule or particle; spatially segregating at least a portion of the capture objects subjected to the immobilizing step into a plurality of separate locations comprising a plurality of reaction vessels such that statistically only zero or one capture object is located in a reaction vessel; sealing the reaction vessels after the addition of the capture objects and optional precursor labelling agent; addressing at least a portion of the plurality of locations subjected to the spatially segregating step and determining the number of said locations containing at least one analyte molecule or particle by, in the case of direct detection, interrogating and/or detecting a molecule or moiety that is comprised in the analyte molecule or particle or, in the case of indirect detection, by interrogating and/or detecting a molecule or moiety that is comprised in a labelling agent that has been converted from a precursor labelling agent by exposure to the analyte molecule or particle; and determining a measure of the concentration of analyte molecules or particles in the fluid sample based at least in part on the number of locations determined to contain at least one analyte molecule or particle. exposing a plurality of capture objects that each include a binding surface having affinity for at least one type of analyte molecule or particle, to a solution containing or suspected of containing the at least one type of analyte molecules or particles; immobilizing analyte molecules or particles with respect to the plurality of capture objects such that at least some of the capture objects associate with at least one analyte molecule or particle and a statistically significant fraction of the capture objects do not associate with any analyte molecule or particle; spatially segregating at least a portion of the capture objects subjected to the immobilizing step into a plurality of separate locations comprising a plurality of reaction vessels such that statistically only zero or one capture object is located in a reaction vessel; sealing the reaction vessels after the addition of the capture objects and optional precursor labelling agent; addressing at least a portion of the plurality of locations subjected to the spatially segregating step and determining the number of said locations containing at least one analyte molecule or particle by, in the case of direct detection, interrogating and/or detecting a molecule or moiety that is comprised in the analyte molecule or particle or, in the case of indirect detection, by interrogating and/or detecting a molecule or moiety that is comprised in a labelling agent that has been converted from a precursor labelling agent by exposure to the analyte molecule or particle; and determining a measure of the concentration of analyte molecules or particles in the fluid sample based at least in part on the number of locations determined to contain at least one analyte molecule or particle.