This thesis examines the potential of neural networks (NN) for forecasting of macroeconomic time series in comparison with linear models. The emphasis is on the autoregressive neural network (ARNN) model, which can be seen as a generalisation of the conventional autoregressive (AR) model where the non-linear part is implemented by a neural network of the feedforward type.Among the properties of macroeconomic time series that motivate various adaptations and enhancements both of linear and of neural network methodology are the following: high stochasticity, short length, non-stationary and seasonal behaviour and the fact that the existence of non-linearity is not clearly known a priori. The development and evaluation of the methods is based on simulated time series with known non-linear properties and on two macroeconomic time series: Austrian unemployment rate and Austrian industrial production index. Both series are in monthly observations and are seasonally unadjusted.After the introduction, the first main chapter of the thesis summarizes the basic concepts of linear univariate time series analysis and applies the linear methodology to the two selected macroeconomic time series. Particular attention is devoted to the problem of finding the appropriate differencing filter -conventional differences, seasonal differences or both -as a way to induce stationarity. Amongst other methods unit root tests are employed. The used linear models are the autoregressive (AR) and the autoregressive moving average (ARMA) model. These are augmented by a model part for deterministic seasonality. The models estimated on the two time series have rather high model order and, despite using a sparse modelling technique, comprise relatively many coefficients.The second main chapter treats various theoretic aspects and types of nonlinearity and carries out a sequence of hypothesis tests for non-linearity, in order to be able to rate the possible benefits of applying neural network methods to the two selected time series. The results of these tests indicate the presence of non-linear structure of the additive type, which can be exploited for better forecasting with ARNN models. However, these results have to be interpreted with care, as they might bei compromised by non-linearity of the multiplicative type, residual linear structure and possible structural breaks.The third main chapter introduces the ARNN model and develops methods for its estimation and specification. The specification contains a model part of determistic seasonality, includes a linear part and allows for sparse specification of coefficients. The generalisation capability of the ARNN model is to be ensured by four alternative model building approaches: the statistical-parametric approach with hypothesis testing and pruning, the classical approach with early stopping, the approach with regularisation and the Bayesian evidence framework. For each one of these approaches modifications and additional heuristics are contributed that seem appropriate in view of the a...