This invention provides novel arylindenopyridines and arylindenopyrimidines of the formula: 1 wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4, and X are as defined above, and pharmaceutical compositions comprising same, useful for treating disorders ameliorated by antagonizing adenosine A2a receptors. This invention also provides therapeutic and prophylactic methods using the instant compounds and pharmaceutical compositions.