The occurrence of alkylphenolic compounds along the Danube River revealed a ubiquitous fingerprint of wastewater impact, recorded in various extents and being the most prominent in the main tributaries and side arms, as well as in vicinity of industrial areas and some Danubian capitals.As revealed by the Joint Danube Survey 2 (JDS2) in 2007, there was a significant decrease in nonylphenol and octylphenol levels in both sediments and suspended particulate matter (SPM) compared to the findings of the Joint Danube Survey 1 (JDS1) in 2001, validating the effects of the EU regulations.Nevertheless, the JDS2 results showed that the inputs of untreated or insufficiently treated wastewater mostly from metropolitan and industrial areas are still large enough to (occasionally) cause nonylphenol concentrations above environmental quality standards (EQS) for freshwater sediments.Nonylphenol mono- and diethoxylates (NP1EO and NP2EO) often coexist with nonylphenol in sediments and SPM in comparable concentrations, which may induce additive mixture effects on Danube biota.Given that there are no EQS for alkylphenolic compounds in SPM, it is difficult to estimate potential risks that SPM-linked contamination may exert on Danube biota. Slight nonylphenol accumulation in mussels was evident at the sites where nonylphenol levels in SPM were continuously high.Based on the JDS2 findings, octylphenol and its lower ethoxylates rarely occur and in low concentrations, thus appear to be of no concern for the Danube environment.Nonylphenol and nonylphenoxyacetic acid (NPE1C) were frequently found in water during the JDS2, exceeding the valid (or proposed) EQS for freshwater in some tributaries. Which possible additive or synergic effects these two compounds may have on aquatic organisms remains however unclear.The results of the Danube surveys highlighted the necessity of reduction of untreated wastewater discharges, especially in areas where alkylphenolic compounds exceeded EQS, in order to protect quality and environmental conditions of the Danube River.