Accessible summary Behaviour that challenges among people with both an intellectual disability and hearing impairment or deafness is common. The aim of our study was to identify factors influencing behaviour (that challenges). We used the Individual Behaviour and Observation Rating Scale to observe and rate behaviour during a period of one year. In this article, we focus on possible relationships between internal factors and behaviour that challenges. We found that social independence, delay of communication and comorbidity of an autism spectrum disorder are possible important risk factors in developing behaviour that challenges. This is important because in clinical practice, we should focus on daily care. Training should be aimed at stimulating social independence and communication skills. Individual training programmes aimed at these skills are therefore essential. Abstract Background: In this article, we describe our study of the prevalence of behaviour that challenges and which internal factors are related to behaviour that challenges in 21 people (fourteen are male, seven are female, varying in age from 12.4 to 42 years; mean 26.6, SD 7.27) with intellectual disabilities who have hearing impairments. Materials and Methods: Data were obtained by recording behaviour on a daily basis during one year using the ‘Individual Behaviour Observation and Rating Scale’ that was developed especially for this study. Results: It was found that 100% of the participants in this study showed behaviour that challenges, although this was not observed every day in each participant. Prevalence rates during a year varied from 1.8% to 77.3%. On average, the prevalence rate was 28.9%. We found a significantly negative correlation between behaviour that challenges and delay of communication as well as the level of social independence. We also found that in people with autism spectrum disorder, the prevalence of behaviour that challenges was significantly higher than in people without autism spectrum disorder. The level of intellectual disability as well as the level of hearing impairments was not related to the prevalence of behaviour that challenges. Conclusion: Because there are several patterns of increasing and decreasing behaviour that challenges throughout the day, it is not possible to draw one conclusion on this issue for the whole group. However, where certain individual patterns can be recognised, it is possible to make individual plans for the clients. This could mean an improvement in daily care and as a result an improvement in the quality of life for people with intellectual disability who have hearing impairments. Implications for clinical practice are discussed.