He studied mathematics and worked with Royal Dutch Shell and some of its operating units as computer programmer and system designer.
Krol"s debut consisted of poems published in 1961 in various Dutch literary magazines. In 1962 his first book De rokken van Joy Scheepmaker was published. Thereafter, he developed a typical writing style consisting of text mingled with abstract thoughts expressed in drawings and mathematical equations.
His novel Het gemillimeterde hoofd is typical for this Krollesque style.
On 20 October 2005, the 125th anniversary of the Amsterdam Free University, Krol received a Doctorate Honoris causa from this university.