In this paper the authors analyze therelationship between personal opinions about the socialsecurity system and levels of informal employment using datafrom a recent household survey carried out in Bulgaria.They compare different indicators of job informality,focusing on the lack of social security affiliation as themain indicator.The results suggest that low value isattached to social security affiliation and that knowledgeof the social security system is very limited.As aconsequence, many workers seem to choose informal jobsbecause they think that the benefits from being affiliatedwith the social security system are too low compared withthe costs. On the other hand, being affiliated does not seemto matter in terms of overall job satisfaction.