The overarching question addressed in the thesis is: What are the relationships between socioeconomic position, parental characteristics, and infant and young child growth and nutrition in urban informal settlements (slums) in Mumbai, India? I answer this question using data from the SNEHA Centres Infant Nutrition Cohort study, an epidemiologic birth cohort of 978 infants born between March 2013 and March 2014 in 20 informal settlements in Mumbai, and followed up till April 2016. After introducing the topic in Chapter 1, I present a systematic review of longitudinal studies in Chapter 2 to identify the determinants of linear growth in infancy and early childhood. Chapter 3 details the cohort's study design, implementation, and data collection procedures. In Chapter 4 I describe how I used these data to derive my main study variables. Chapter 5 presents a profile of the cohort at birth, outlining key infant, parental and household socioeconomic characteristics. I also investigate patterns and predictors of missing data and non-response in longitudinal data. In Chapter 6 I identify the determinants of linear growth between 0-37 months using the SITAR model to fit growth curves to 16 753 length measurements for 944 children. I quantify the relationship between parental anthropometry and child growth. In Chapter 7 I describe infant and young child feeding practices, and investigate the relationships between baseline characteristics and longitudinal feeding patterns using discrete-time survival and dynamic autoregressive models. In Chapter 8 I investigate whether the relationship between predominant breastfeeding (0-5 months) and predicted length at 24 months is mediated by consumption of animal source foods at 6-23 months using causal mediation analysis. Chapter 9 begins with a summary of the main findings of my research. I discuss the empirical and methodologic implications of my study.