Studies have shown that inadequate care, also referred to as abuse, violence, neglect and maltreatment occur in nursing homes in many countries. The aim of this study was to describe the frequency and types of inadequate care committed by staff in nursing homes. Another aim was to investigate if nursing staff reported differently depending on age, education level and years of experience working at nursing homes. A questionnaire survey was conducted among nursing staff (n = 616) in 16 nursing homes in the central part of Norway. Twenty items concerned staff behaviour in forms of acts of inadequate care. The respondents were asked to report how often they had observed colleagues commit acts and how often they themselves had committed such acts. The response rate was 79%. All in all, 91% of the nursing staff reported that they had observed at least one act of inadequate care and 87% reported that they had committed at least one act of inadequate care. Acts of negligent and emotional character were most frequently reported, both as observed and committed. Depending on the higher educational level that the nursing staff had more acts of all types were observed and committed. The oldest staff and those with longest experience at the present nursing home reported more observed and committed acts of physical character than did the others. The extent of inadequate care confirms that this is a common part of activities in nursing homes. Because emotional and negligent acts can be just as harmful as physical acts, more knowledge is needed about the reasons in order to take preventive actions.