Surface microlayer (SM) samples were collected with a rotating cylinder sampler from the York and Elizabeth River estuaries of lower Chesapeake Bay bimonthly from May 1994 through June 1995. Two intensive samplings were also conducted in the York River during different seasons: one in December 1994 and another during June 1995. Four SM samples were collected during each intensive sampling within 4 days. All the samples were analyzed for total suspended particulates (TSP), particulate nitrogen (PN), particulate organic carbon (POC) and dissolved organic carbon (DOC). The thickness of the SM was observed to decrease linearly with increased wind speed. TSP and POC in the SM were found to be enriched up to 1000-fold over the corresponding subsurface water, and to be exponentially related with wind speed at sampling. Enrichment of DOC in the SM relative to subsurface bulk water was also observed at both sampling sites. Larger average POC/PN ratios and consistently smaller particle sizes were observed in the Elizabeth River compared with the York River, suggesting that the former is heavily influenced by atmospheric deposition, as well as urban and terrestrial runoff, whereas in situ production of particles dominates in the latter. No seasonal trends were observed in the SM characteristics with the exception of particle size fractions in the York River, which fluctuate seasonally presumably due to changes in the dominant phytoplankton species. TSP and POC concentrations in the SM can be described by a first-order wind-driven mixing model. Wind-driven mixing of SM DOC was less apparent than for TSP and POC. ¿ 1998 American Geophysical Union