The influence of factors in catching and processing of cod on fillet yield, gaping, number of nematodes and prevalence of bruises was studied in close cooperation with an Icelandic fisheries company. Data was collected onboard fishing vessels and in a fish processing plant in N-Iceland, for 29 months. Conditions during trawling and storing were recorded. Fishing ground had significant effect (95% significance limit) on fillet yield, gaping and number of parasites. Time of year had significant effect on all variables. The time-lag from catch to processing (age of the raw material) affected both gaping and bruises significantly. Fillet yield was closely correlated to both condition factor and head proportion. The results can be used for decision-making on where to direct the fishing boats and what to do with the catch after unloading it. (c) 2006 Elsevier Ltd. All rights reserved.