For each faithful finite
dimensional irreducible representation R of a finite dimensional simple Lie
algebra L over the complex field, this paper treats the integrally parameterized
subgroup GZ of the Chevalley Group G over the rational field Q. For L of
type Al,Dl, or El, Lie algebraic methods are used to extend a result of J.
Nielson on SL(S,Z) to obtain a finite set of defining relations for GZ. Similar
relations augmented by defining relations for rτYz∖(B2) are shown to define GZ
when L is of type Bl,Cl, or F4. (The relations for GZ(B2) are not listed
here.)