The abundance of sulphate-reducing bacteria (SRB) in oilfield waters from six land-based flowstations at different oilfields in the Niger Delta of Nigeria was determined over a period of six months, using the most probable number technique. All the oilfield waters contained SRB. However their relative abundances varied with month of sampling. The highest count (2400 SRB/100 ml) was obtained during the rainy season months (July/August) while the lowest SRB density (9 SRB/100 ml), which also corresponded with lowest values of oil and grease content of the oilfield waters, was obtained during the dry season (November/December). The presence of SRB in such large numbers in the oilfield water samples showed that the waters had the potential to sustain the growth of the organisms and their prevalence suggested that these organisms could be a source of crude oil contamination and biocorrosion of pipe- and flow-lines.