To attack certain problems in 4-dimensional knot theory the author draws on a variety of techniques, focusing on knots in S^T4, whose fundamental groups contain abelian normal subgroups. Their class contains the most geometrically appealing and best understood examples. Moreover, it is possible to apply recent work in algebraic methods to these problems. New work in four-dimensional topology is applied in later chapters to the problem of classifying 2-knots.