Specified phenylpropionic acid derivatives and analogues thereof have an antagonistic activity to &agr; 4 integrin. They are used as therapeutic agents or preventive agents for various diseases concerning &agr; 4 integrin, such as inflammatory diseases in which &agr; 4 integrin-depending adhesion process participates in the pathology, rheumatoid arthritis, inflammatory bowel diseases, systemic lupus erythematosus, multiple sclerosis, Sjögren's syndrome, asthma, psoriasis, allergy, diabetes, cardiovascular diseases, arterial sclerosis, restenosis, tumor proliferation, tumor metastasis and transplantation rejection.