The effectiveness of "Investors in People," which was launched in October 1991 as the United Kingdom's national standard for training and development, was evaluated through a 3-year longitudinal study that included interviews with a sample of 1,804 employers and a series of case study interviews. Of the 1,804 employers interviewed, 76.6% were in the private sector, 35.6% represented the production sector, and 64.4% represented the services sector. Included in the sample were employers employing as few as 1-9 employees and as many as 1,000 or more employees. Some of the employers were interviewed for the first time in 1995, whereas others had been interviewed during 2 or all 3 years of the longitudinal study. The study focused on employers' reasons for becoming involved with Investors in People, problems with achieving/maintaining the standard, and Investors in People's impact on their practice and business performance. Overall, Investors in People was found to be a successful initiative that delivers better training and skills, tackles problems not reached by other initiatives, and pays for itself by providing better value from training expenditure and, ultimately, fewer skill shortages and increased profitability. (Forty-eight tables/figures are included. Appended are detailed descriptions of the research methodology and regression results.) (MN)