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Increasing commercial application of silver nanoparticles (Ag NP) and subsequent presence in wastewater and sewage sludge has raised concerns regarding their effects in the aquatic and terrestrial environment. Several studies have employed standardised acute and chronic earthworm-based tests to establish the toxicological effects of Ag NP within soil. These studies have relied heavily on the use of epigiec earthworm species which may have limited ecological relevance in mineral soil. This study assessed the influence of Ag NP (uncoated 80 nm powder) and AgNO 3 on survival, change in biomass and avoidance behaviour in a soil dwelling (endogiec) species, Allolobophora chlorotica . Earthworms were exposed for 14 days to soils spiked with Ag NP or AgNO 3 at 0, 12.5, 25, 50 and 100 mg kg −1 either separately for survival and biomass measurement, or combined within a linear gradient to assess avoidance. Avoidance behaviour was shown to provide the most sensitive endpoint with an observable effect at an Ag NP/AgNO 3 concentration of 12.5 mg kg −1 compared with 50 mg kg −1 for biomass change and 100 mg kg −1 for survival. Greater mortality was observed in AgNO 3 (66.7%) compared with Ag NP-spiked soils (12.5%) at 100 mg kg −1 , attributed to increased presence of silver ions. Although comparison of results with studies employing Eisenia fetida and Eisenia andrei suggest that the A. chlorotica response to Ag NP is more sensitive, further research employing both epigeic and endogeic earthworms under similar experimental conditions is required to confirm this observation. [ABSTRACT FROM AUTHOR]