The influence of substitutional disorder, of random forces and of energy dissipation on solitons in alternating trans-polyacetylene using the Su-Schrieffer-Heeger Hamiltonian is discussed. Double ionization in polyene chains was also investigated. Further soliton dynamics within a full Pariser-Parr-Pople Hamiltonian for trans-polyacetylene are presented. The presence of conformational solitons in stacked systems is shown numerically in a polyformamide model system. Possible relations to DNA and carcinogenesis are briefly reviewed.