Pyrimidines of formula (I): ##STR00001## wherein R.sup.1 to R.sup.4, X and Y are defined in the specification are inhibitors of P13K and may thus be used to treat diseases and disorders arising from abnormal cell growth, function or behavior associated with P13 kinase such as cancer, immune disorders, cardiovascular disease, viral infection, inflammation, metabolism/endocrine function disorders and neurological disorders.