This Technical Specification offers guidance on statistical methods used for the analysis of data of standardized ecotoxicity tests. It focuses on statistical methods for obtaining statistical estimates of parameters in current and future use, e.g. ECx (LCx), NOEC, NEC. The methods described are intended to cover laboratory ecotoxicity tests (aquatic, sediment and/or terrestrial tests), and may also be relevant for other toxicity tests. The main objective of this Technical Specification is to provide practical guidance on how to analyse the observations from ecotoxicity tests. Hypothesis testing, concentration-response modelling and biology-based modelling are discussed for the different data types (quantal, continuous and discrete data, corresponding to mortality, growth or reproduction). In addition, some guidance on experimental design is given. Although the main focus is on giving assistance to the experimentalist, a secondary aim is to help those who are responsible for evaluating toxicity tests. Finally, the document may be helpful in developing new toxicity test guidelines by giving information on experimental design and statistical analysis issues.