MBL Awards are given for the best paper presented at the General Scientific Meetings by a senior investigator, a junior investigator, a graduate student, and an undergraduate; additional papers are selected for Honorable Mention. The five presentations selected for MBL Awards this year reflect the broad scope of science at the Laboratory. Among these reports we find that lipopolysaccharide, the prime cause of gram-negative bacterial toxicity, occurs in eukaryotes; that a long-term decrease in synaptic strength is induced by a transient suppression of NMDA receptor activity; that cis editing in a trypanosome is a model of guide-RNA structure and function; that a female lobster's sperm load affects her choice of a mate; and that enzyme activities can be used to assess the stimulatory effect of increased estuarine nitrogen on the growth of sea lettuce. This year's awardees are listed below with the title of their presentation and the page on which their abstract appears. -The Editor August 2004.