The Republic of Mozambique is experiencing a significant social and economic change and needs an updated informative base to allow policy-makers to found their decision on reliable and comparable data. The fast development of the Non Observed Economy (NOE) was one of the most important consequences of the transformation of the Mozambican economy. The Italian support Programme to the Mozambique National Statistical System , started in 2004, provided technical assistance for improving the quality of statistics for the Mozambican government according to best practices and international standards. One of the most interesting component of the project was the definition of a methodology for the analysis of the NOE and the provision of a first estimate of the phenomenon through a survey carried out at national level. Within the consortium, led by ICstat, Istat was responsible for the component, with the technical support of experts from INE Mozambique and INE Portugal . The NOE, as defined in the OECD Handbook for Measuring the Non Observed Economy, is one of the most relevant issues to be tackled in order to guarantee a correct comparison of the National Accounts variables and the exhaustiveness of National Accounts estimates, according to the System of National Accounts defined by the UN Handbook (SNA93), nowadays adopted by the majority of countries, that allows the correct comparison of their economic results. At international level there has been considerable progress towards the harmonization of statistical concepts and methods, through the adoption by international organizations of common standards and recommendations: 15th International Conference of Labour Statistics – Recommendation on employment statistics in the informal sector (1993); 3rd Revision of the United Nation’s System of National Accounts, which indicated how the informal sector should be treated in the accounts; the OECD Handbook, which also draws on the SNA93 for the terms used in the definition of NOE. Statistical information about the informal sector and small enterprises in Mozambique is still very sketchy in spite of their major economic significance: the informal sector is in fact directly linked to the main objectives of development (increased production, job creation, combating poverty). Therefore, strong attention has been paid to this component and in particular to the implementation of a specific survey for gathering the information necessary for the assessment of the methodology and the estimation of the sector. In this sense, the main commitment of the project was to strengthen INE Mozambique’s statistical capacity, in order both to approach the NOE sector according to international standards and to carry out, for the first time, a survey based on sound and exhaustive methodology. The aim of this handbook is twofold: • To focus on the experience derived from the project’s component, describing the strategies adopted and the steps implemented to define an ad-hoc methodology within the social and economic contextual factors which takes into account the national statistical environment and the international statistical framework (international standards, assessment of the Informal Sector in Mozambique, questionnaire, survey techniques and final estimations). The methods and techniques presented for approaching the informal sector study could represent a reference for future analysis on this phenomenon and for repeating similar surveys. • To present the results of the survey with the main information on the sector and a first analysis of it. Although the Mozambique reality represents a peculiar case, the value added of the project’s component lies in the fact that the experiences gained and the good practices adopted can be a reference model for those countries that are currently experiencing a development phase with socio-economic features comparable with those of the Mozambican economy. The results of the survey are useful for more exhaustive estimations for National Accounts and, at the same time, represent a benchmark of social evaluation for planning poverty reduction strategies (PARPA). Moreover, with this survey INE Mozambique has analysed the agricultural production (in most cases represented by “production for auto-consumption”), often coming from secondary activities of households which are located in the urban area and that, as main activity, conduct extra-agricultural activities.