The aim of this study is to determine functioning of in-service training activities according to teachers’ opinions. Descriptive survey method was used. The study group consists of 304 teachers working at high schools in Altındag district in Ankara province. Convenience sampling was used. A data gathering tool consist of two parts was used to collect data. According to research findings, it was found that arithmetic mean of the teachers’ agreement level in the positive opinions about functioning of in-service training activities was 2.74 (undecided) and arithmetic mean of agreement level of negative opinions was 2.72 (undecided). There is a significant difference between opinions of teachers about functioning of in-service training activities according to gender but there is no significant difference according to school which they works and in-service training activities they attended. There is no significant difference between teachers positive opinions in terms of functioning of in-service training activities according to working period but there is significant difference between negative opinions.
İn-service training, on the job training, life-long education