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This thesis presents results of laboratory investigations of stratospheric dust that have a direct bearing on the theory of cometary panspermia. Chapter 1 deals with the historical backdrop to panspermia theories, with a summary of recent relevant work on comets, meteorites and IDP's (Interplanetary Dust Particles). In Chapter 2 I describe the techniques that have been used over several decades to collect stratospheric dust with a view to identifying a cometary and possible biological components. The Cryosampler technique deployed by ISRO in 2001 provides the best hope for preserving small fragile particles of cometary origin, even those of possible biological provenance. The source material for my laboratory investigations was collected using the Cryosampler technique in a balloon flight on 21 January 2001. The description of techniques for stratospheric air collection, extraction of aerosols, analysis by SEM, EDX and the results of my investigations using these techniques form the main bulk of Chapter 3. Over 30 individual IDP's were imaged, analysed, catalogued and classified. Many biologically relevant particles including putative bacterial spores and nanobacteria were discovered. In Chapter 4 DNA extracts from the stratospheric samples were analysed using PCR amplification of 16S rRNA gene sequences. Evidence of actinobacteria (96% homology) and chloroplast sequences (99% homology) point to an extraterrestrial origin of these genes. Arguments for contamination are discussed, and ruled out. In Chapter 5 present a preliminary analysis of the 2001 Kerala Red Rain samples. SEM, TEM images were obtained, and staining tests for DNA carried out. The origin of the red rain cells remains inconclusive.