Your supplement “Career choices for scientists” describes some of the interesting moves out of the lab that researchers make from necessity or choice (Nature 402 (Suppl.), 11 November 1999). Does anyone do the reverse? Are there scientists who acquired a science degree after their mid-twenties, say, but who made it into full-time research? With the huge growth in education for mature students in the past 30 years there are many thousands with degrees acquired later rather than earlier. Do significant numbers of them reach the research lab?