The concept of generating liquid crystalline polymer (LCP) reinforcing fibrils on an in situ basis has a number of potentially attractive advantages over the use of the more commonly used glass-reinforced composites. The potential advantages include a wider range of processing options, improved surface appearance, recyclability, and lower processing energy requirements. Many of these advantages have been discussed in previous reviews such as those written by Dutta et al. [1] and La Mantia and Valenza [2]. However, to successfully compete with glass-reinforced thermoplastics, in situ composites based on thermoplastics reinforced with thermotropic LCPs (TLCPs) should at least exhibit similar properties to injection-molded glass-reinforced thermoplastics. One purpose of this review is to address the advantages and disadvantages of in situ composites, and the other is to provide some standards for comparison against more commonly used composites.