The institution of large-scale international cooperative research programs in the study of ocean systems has made more rigorous quality control over analytical procedures necessary. A series of intercalibration and intercomparison exercises have shown that increased care is needed in running even those determinations which have been run for years, and are considered as “standard” methods. Care in sampling is needed to ensure that the various samplers used are sampling for the same materials. At this time, we do not know the scale of heterogeneity to be expected in the open ocean, and so must eliminate as many sources of error as possible from our analytical and sampling schemes, since what differences are left will be assigned to the environment.