For the routine determination of organic matter in marine sediment, a
rough estimate is often obtained by measuring the loss of weight on ig
nition (Difference-On-Ignition method: D.O.I.). This D.O.I. is to be u
sed in ecological studies where organic material in sediment is used a
s an environmental variable among others. A review of papers using thi
s method showed a great variability within conditions used. These cond
itions are generally used without accurate justification. We propose a
simple standard procedure based on grain-size fraction of sediment to
determine optimal temperature and time of ignition, and the influence
of the sample weight. The method proposed, using the loss of weight o
n ignition, will give the same accuracy in measurements of organic mat
ter in marine sediments.