The experimental evidence accumulated over the past 20 years indicaates that text indexing systems based on the assignment of appropriately weighted single terms roduce retrival results that are superior to those obtainable with other more eleborate text representations. These results depend crucially on the choice of effective term weighting systems. This paper summarizes the insights gained in automaticterm weighting,and provides baseline single term indexing models eith which other more eleborate content analysis produres can be compared.