This paper provides a tutorial review of modulation recognition techniques. The available modulation recognizers are classified into three main categories. The first category is concerned with the analog modulations only. The second category is concerned with the digital modulations only. The third category is concerned with botlf-analog and digital modulation without any prior information about the nature of a signal. Comparisons between the available modulation recognizers in each category are developed. Some of these modulation recognizers utilize the decision-theoretic approach, some utilize the pattern recognition, some combine both approaches and the rest utilize the ANNs approach.