The importance of perceived quality and brand loyalty is increasing recently both domestic and foreign. So many papers perform research on service quality and brand loyalty. Today, there is the rapid growth in the Korean mobile telecommunications service market. But mobile telecommunications service companies don't pay full attention to customers' attitude and brand loyalty. This paper shows why Korean mobile telecommunications service companies have to focus on Brand Loyalty. This paper investigates the relationship among perceived quality, attitude and brand loyalty in the area of mobile telecommunications service.