The present invention relates to a .beta..sub.3 adrenergic receptor agonist of formula (I), wherein R is C.sub.3 C.sub.8 alkyl or (C.sub.3 C.sub.7 cycloalkyl)C.sub.1 C.sub.5 alk-di-yl: R.sup.1 is H, CN, halo; C.sub.1 C.sub.6 alkyl, C.sub.1 C.sub.4 haloalkyl, CO.sub.2 R.sup.6, CONR.sup.6R.sup.6, NR.sup.6COR.sup.7, NR.sup.6R.sup.6, OR.sup.6, SR.sup.6, SOR.sup.7, S0.sub.2R.sup.7 or SO.sub.2NR.sup.6R.sup.6; R.sup.1a is H, halo or C.sub.1 C.sub.6 alkyl; R.sub.2 is H or C.sub.1 C.sub.6 alkyl; R.sup.3 and R.sup.4 are independently H or C.sub.1 C.sub.6 alkyl R.sup.5 is hydrogen, optionally substituted phenyl or optionally substituted heterocycle; X is absent or is OCH.sub.2 or SCH.sub.2; X.sup.1 is absent or C.sub.1 C.sub.5 alk-di-yl; and X.sup.2 is absent or is O, S, NH, NHSO.sub.2, SO.sub.2NH or CH.sub.2; or a pharmaceutical salt thereof; which is capable of increasing lipolysis and energy expenditure in cells and, therefore, is useful for treating Type 2 diabetes and/or obesity ##STR00001##