Nuclear lamins were initially identified as the major components of the nuclear lamina, a proteinaceous layer found at the interface between chromatin and the inner nuclear membrane (Fawcett 1966). Due to their position at the periphery of the nucleus, lamins were originally proposed to support the nuclear envelope and provide anchorage sites for chromatin. Recently, the nuclear lamins have also been found in the nucleoplasm (Fig. 1). In addition, experimental and genetic evidence suggest that nuclear lamins are involved in a number of other functions including nuclear envelope assembly, DNA synthesis, transcription, and apoptosis. Interestingly, mutations in nuclear lamins have been linked to human diseases. In this review, we describe what is known of the structure and function of lamins and their associated proteins. Further, we speculate about possible mechanisms through which mutations in nuclear lamins give rise to disease. Immunological and structural data originally suggested that the lamins were related to cytoplasmic intermediate filaments (IF)(Aebi et al. 1986; Goldman et al. 1986). The cloning and sequencing of lamin cDNAs confirmed that lamins have the typical domain structure of IF including an α-helical coiled-coil domain flanked by nonhelical domains (Fisher et al. 1986; Mc-Keon et al. 1986). Interestingly, analyses of lamin and cytoplasmic IF genomic sequences indicate that nuclear lamins are the progenitors of all IF, with cytoplasmic IF arising through gene duplication (Riemer et al. 2000).